U.S. patent application number 17/419761 was filed with the patent office on 2022-03-24 for additive manufacturing using materials that form a weak gel.
This patent application is currently assigned to Stratasys Ltd.. The applicant listed for this patent is Stratasys Ltd.. Invention is credited to Nissim DAVID, Daniel DIKOVSKY.
Application Number | 20220089868 17/419761 |
Document ID | / |
Family ID | 1000006055154 |
Filed Date | 2022-03-24 |
United States Patent
Application |
20220089868 |
Kind Code |
A1 |
DIKOVSKY; Daniel ; et
al. |
March 24, 2022 |
ADDITIVE MANUFACTURING USING MATERIALS THAT FORM A WEAK GEL
Abstract
A formulation usable in additive manufacturing of a
three-dimensional object is provided. The formulation comprises one
or more monofunctional curable material(s); one or more hydrophilic
multifunctional curable material(s); and one or more water-miscible
non-curable material(s), such that a total amount of the curable
materials is 20% or less, by weight, and a weight ratio of a total
weight of the monofunctional curable material(s) and a total weight
of the hydrophilic multifunctional curable material(s) ranges from
1:1 to 10:1. The formulation features, when hardened, properties of
a weak and flowable gel. Additive manufacturing processes utilizing
the formulation as a support material formulation are also
provided.
Inventors: |
DIKOVSKY; Daniel; (Ariel,
IL) ; DAVID; Nissim; (Netanya, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stratasys Ltd. |
Rehovot |
|
IL |
|
|
Assignee: |
Stratasys Ltd.
Rehovot
IL
|
Family ID: |
1000006055154 |
Appl. No.: |
17/419761 |
Filed: |
December 31, 2019 |
PCT Filed: |
December 31, 2019 |
PCT NO: |
PCT/IL2019/051441 |
371 Date: |
June 30, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62786809 |
Dec 31, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29K 2105/0061 20130101;
B33Y 70/00 20141201; B29C 64/124 20170801; C08L 71/02 20130101;
B33Y 10/00 20141201; B29C 64/40 20170801; C08L 2205/035
20130101 |
International
Class: |
C08L 71/02 20060101
C08L071/02; B29C 64/124 20170101 B29C064/124; B29C 64/40 20170101
B29C064/40; B33Y 10/00 20150101 B33Y010/00; B33Y 70/00 20200101
B33Y070/00 |
Claims
1. A formulation usable in additive manufacturing of a
three-dimensional object, the formulation comprising: at least one
monofunctional curable material; at least one hydrophilic
multifunctional curable material; and at least one water-miscible
non-curable material, wherein: a total amount of said at least one
monofunctional curable material ranges from 1 to 10, or from 3 to
10, or from 5 to 10, % by weight, of the total weight of the
formulation; a total amount of the curable materials is 20% or
less, by weight, of the total weight of the formulation; and a
weight ratio of a total weight of said at least one monofunctional
curable material and a total weight of said at least one
hydrophilic multifunctional curable material ranges from 1:1 to
10:1.
2. (canceled)
3. The formulation of claim 1, wherein: a total amount of said at
least one hydrophilic multifunctional curable material ranges from
1 to 5, % by weight, of the total weight of the formulation.
4. The formulation of claim 1, wherein said at least one
hydrophilic multifunctional curable material provides, when
hardened per se, a material that is water insoluble.
5. The formulation of claim 1, wherein at least one of said
monofunctional curable material(s) comprises a hydrophilic
monofunctional curable material.
6. The formulation of claim 1, wherein at least one of said
monofunctional curable material(s) comprises a hydroxyalkyl and/or
an alkylene glycol moiety.
7. The formulation of claim 1, wherein at least one of said
hydrophilic multifunctional curable material(s) comprises one or
more alkylene glycol moieties.
8. (canceled)
9. The formulation of claim 1, wherein said at least one
non-curable material comprises a polymeric material.
10. The formulation of claim 9, wherein said at least one
non-curable material further comprises a non-polymeric
material.
11. The formulation of claim 10, wherein a weight ratio of a total
weight of said at least one polymeric non-curable material and a
total weight of said at least one non-polymeric non-curable
material ranges from 2:1 to 1:2.
12. The formulation of claim 1, comprising: said at least one
monofunctional curable material, in an amount of from 3 to 10, % by
weight; said at least one multifunctional curable material in an
amount of from 3 to 5, % by weight; at least one polymeric
non-curable material in an amount of from 30 to 60, % by weight;
and at least one non-polymeric non-curable material in an amount of
from 30 to 60, % by weight, wherein a total amount of said
non-curable materials is at least 80% by weight.
13. The formulation of claim 1, being devoid of water.
14. The formulation of claim 1, featuring a viscosity of from 8 to
40 centipoises at 75.degree. C.
15-16. (canceled)
17. The formulation of claim 1, featuring, when hardened, a gel
material that is flowable upon application of positive
pressure.
18-20. (canceled)
21. The formulation of claim 1, further comprising a
photoinitiator.
22. The formulation of claim 21, wherein an amount of said
photoinitiator is no more than 2% by weight of the total weight of
the formulation.
23. A method of additive manufacturing of a three-dimensional
object, the method comprising sequentially forming a plurality of
layers in a configured pattern corresponding to the shape of the
object, thereby forming the object, wherein the formation of at
least a few of said layers comprises: dispensing at least two
building material formulations, said at least two building material
formulations comprise a modeling material formulation M which, upon
exposure to a curing condition, forms a hardened modeling material
M, and a formulation according to claim 1, which, upon exposure to
said curing condition, forms a hardened support material FG.
24. The method of claim 23, wherein said dispensing is such that
said hardened modeling material M forms at least one hollow
structure, and said material FG is at least partially enclosed in
said hollow structure.
25-27. (canceled)
28. A method of additive manufacturing of a three-dimensional
object having a cavity, the method comprising sequentially forming
a plurality of layers in a configured pattern corresponding to a
combined shape of the object and a sacrificial object, in a manner
that said sacrificial object is enclosed in by a sacrificial shell,
and said sacrificial shell is enclosed in said cavity; and removing
said sacrificial object and said sacrificial shell from said
cavity; wherein said sacrificial object comprises a modeling
material M, and said sacrificial shell is made of a support
material FG formed of the formulation according to claim 1.
29. The method according to claim 28, wherein said sacrificial
object also comprises said FG material, said FG material being
reinforced by said modeling material M.
30. The method according to claim 29, wherein said modeling
material M occupies from about 20% to about 40% of a volume of said
sacrificial object.
Description
RELATED APPLICATION
[0001] This application claims the benefit of priority of U.S.
Provisional Patent Application No. 62/786,809 filed on Dec. 31,
2018, the contents of which are incorporated herein by reference in
their entirety.
FIELD AND BACKGROUND OF THE INVENTION
[0002] The present invention, in some embodiments thereof, relates
to additive manufacturing and, more particularly, but not
exclusively, to curable formulations which provide, when hardened,
materials featuring properties of a weak gel, and to additive
manufacturing of three-dimensional objects using same.
[0003] Additive manufacturing (AM) is generally a process in which
a three-dimensional (3D) object is manufactured utilizing a
computer model of the objects. Such a process is used in various
fields, such as design related fields for purposes of
visualization, demonstration and mechanical prototyping, as well as
for rapid manufacturing (RM). The basic operation of any AM system
consists of slicing a three-dimensional computer model into thin
cross sections, translating the result into two-dimensional
position data and feeding the data to control equipment which
manufacture a three-dimensional structure in a layerwise
manner.
[0004] One type of AM is three-dimensional inkjet printing
processes. In this process, a building material is dispensed from a
dispensing head having a set of nozzles to deposit layers on a
supporting structure. Depending on the building material, the
layers may then be cured or solidified using a suitable device.
[0005] Various three-dimensional inkjet printing techniques exist
and are disclosed in, e.g., U.S. Pat. Nos. 6,259,962, 6,569,373,
6,658,314, 6,850,334, 7,183,335, 7,209,797, 7,225,045, 7,300,619,
7,479,510, 7,500,846, 7,962,237.
[0006] Several AM processes allow additive formation of objects
using more than one modeling material. For example, U.S. Pat. No.
9,031,680 of the present Assignee, discloses a system which
comprises a solid freeform fabrication apparatus having a plurality
of dispensing heads, a building material supply apparatus
configured to supply a plurality of building materials to the
fabrication apparatus, and a control unit configured for
controlling the fabrication and supply apparatus. The system has
several operation modes. In one mode, all dispensing heads operate
during a single building scan cycle of the fabrication apparatus.
In another mode, one or more of the dispensing heads is not
operative during a single building scan cycle or part thereof.
[0007] The building materials may include modeling materials and
support materials, which form the object and the temporary support
constructions supporting the object as it is being built,
respectively.
[0008] The modeling material, also referred to herein as "model
material", (which may include one or more material(s), included in
one or more formulations) is deposited to produce the desired
object/s.
[0009] The support material, also known in the art as "supporting
material", (which may include one or more material(s)) is used,
with or without modeling material elements, is used to support
specific areas of the object during building and for assuring
adequate vertical placement of subsequent object layers. For
example, in cases where objects include overhanging features or
shapes, e.g. curved geometries, negative angles, voids, and the
like, objects are typically constructed using adjacent support
constructions, which are used during the printing.
[0010] In all cases, the support material is deposited in proximity
of the modeling material, enabling the formation of complex object
geometries and filling of object voids.
[0011] In all of the currently practiced technologies, the
deposited support material and modeling material are hardened,
typically upon exposure to a curing condition (e.g., curing
energy), to form the required layer shape. After printing
completion, support structures are removed to reveal the final
shape of the fabricated 3D object.
[0012] When using currently available commercial print heads, such
as ink-jet printing heads, the support material should have a
relatively low viscosity (about 10-20 cPs) at the working, i.e.,
jetting, temperature, such that it can be jetted. Further, the
support material should harden rapidly in order to allow building
of subsequent layers. Additionally, the hardened support material
should have sufficient mechanical strength for holding the model
material in place, and low distortion for avoiding geometrical
defects.
[0013] Known methods for removal of support materials include
mechanical impact (applied by a tool or water-jet), as well as
chemical methods, such as dissolution in a solvent, with or without
heating. The mechanical methods are labor intensive and are often
unsuited for small intricate parts.
[0014] For dissolving the support materials, the fabricated object
is often immersed in water or in a solvent that is capable of
dissolving the support materials. The solutions utilized for
dissolving the support material are also referred to herein and in
the art as "cleaning solutions". In many cases, however, the
support removal process may involve hazardous materials, manual
labor and/or special equipment requiring trained personnel,
protective clothing and expensive waste disposal. In addition, the
dissolution process is usually limited by diffusion kinetics and
may require very long periods of time, especially when the support
constructions are large and bulky.
[0015] Furthermore, post-processing may be necessary to remove
traces of a `mix layer` on object surfaces. The term "mix layer"
refers to a residual layer of mixed hardened model and support
materials formed at the interface between the two materials on the
surfaces of the object being fabricated, by model and support
materials mixing into each other at the interface between them.
[0016] Additionally, methods requiring high temperatures during
support removal may be problematic since there are model materials
that are temperature-sensitive, such as waxes and certain flexible
materials. Both mechanical and dissolution methods for removal of
support materials are especially problematic for use in an office
environment, where ease-of-use, cleanliness and environmental
safety are major considerations.
[0017] Water-soluble materials for 3D building are described, for
example, in U.S. Pat. No. 6,228,923, where a water soluble
thermoplastic polymer--Poly(2-ethyl-2-oxazoline)--is taught as a
support material in a 3D building process involving high pressure
and high temperature extrusion of ribbons of selected materials
onto a plate.
[0018] A water-containing support material comprising a fusible
crystal hydrate is described in U.S. Pat. No. 7,255,825.
[0019] Formulations suitable for forming a hardened support
material in building a 3D object are described, for example, in
U.S. Pat. Nos. 7,479,510, 7,183,335 and 6,569,373, all to the
present Assignee. Generally, the compositions disclosed in these
patents comprise at least one UV curable (reactive) component,
e.g., an acrylic component, at least one non-UV curable component,
e.g. a polyol or glycol component, and a photoinitiator. After
irradiation, these compositions provide a semi-solid or gel-like
material capable of dissolving or swelling upon exposure to water,
to an alkaline or acidic solution or to a water detergent
solution.
[0020] Besides swelling, another characteristic of such a support
material may be the ability to break down during exposure to water,
to an alkaline or acidic solution or to a water detergent solution
because the support material is made of hydrophilic components.
During the swelling process, internal forces cause fractures and
breakdown of the hardened support. In addition, the support
material can contain a substance that liberates bubbles upon
exposure to water, e.g. sodium bicarbonate, which transforms into
CO.sub.2 when in contact with an acidic solution. The bubbles aid
in the process of removal of support from the model.
[0021] Several additive manufacturing processes allow additive
formation of objects using more than one modeling material. For
example, U.S. Patent Application having Publication No.
2010/0191360, of the present Assignee, discloses a system which
comprises a solid freeform fabrication apparatus having a plurality
of dispensing heads, a building material supply apparatus
configured to supply a plurality of building materials to the
fabrication apparatus, and a control unit configured for
controlling the fabrication and supply apparatus. The system has
several operation modes. In one mode, all dispensing heads operate
during a single building scan cycle of the fabrication apparatus.
In another mode, one or more of the dispensing heads is not
operative during a single building scan cycle or part thereof.
[0022] In a 3D inkjet printing process such as Polyjet.TM.
(Stratasys Ltd., Israel), the building material is selectively
jetted from one or more printing heads and deposited onto a
fabrication tray in consecutive layers according to a
pre-determined configuration as defined by a software file.
[0023] U.S. Pat. No. 9,227,365, by the present assignee, discloses
methods and systems for solid freeform fabrication of shelled
objects, constructed from a plurality of layers and a layered core
constituting core regions and a layered shell constituting envelope
regions.
[0024] Additive Manufacturing processes have been used to form
rubber-like materials. For example, rubber-like materials are used
in PolyJet.TM. systems as described herein. These materials are
formulated to have relatively low viscosity permitting dispensing,
for example by inkjet, and to develop Tg which is lower than room
temperature, e.g., -10.degree. C. or lower. The latter is obtained
by formulating a product with relatively low degree of
cross-linking and by using monomers and oligomers with intrinsic
flexible molecular structure (e.g., acrylic elastomers).
[0025] An exemplary family of Rubber-like materials usable in
PolyJet.TM. systems (marketed under the trade name "Tango.TM."
family) offers a variety of elastomer characteristics of the
obtained hardened material, including Shore A hardness, Elongation
at break, Tear Resistance and Tensile strength.
[0026] Another family of Rubber-like materials usable in
PolyJet.TM. systems (marketed under the trade name "Agilus.TM."
family) is described in PCT International Application No.
IL2017/050604 (Published as WO2017/208238), by the present
assignee, and utilizes a curable elastomeric formulation that
comprises an elastomeric curable material and silica particles.
[0027] PCT International Patent Applications Publication Nos. WO
2019/021291, WO 2019/021292 and WO 2019/021295, all by the present
Assignee, describe formulations that are usable in additive
manufacturing of three-dimensional objects, and which provide, upon
exposure to a curing condition, a liquid or liquid-like
material.
SUMMARY OF THE INVENTION
[0028] According to an aspect of some embodiments of the present
invention there is provided a formulation usable in additive
manufacturing of a three-dimensional object, which is also referred
to herein as an FG formulation, which comprises:
[0029] at least one monofunctional curable material;
[0030] at least one hydrophilic multifunctional curable material;
and
[0031] at least one water-miscible non-curable material,
[0032] wherein a total amount of the curable materials is 20% or
less, by weight, of the total weight of the formulation, and
wherein a weight ratio of a total weight of the at least one
monofunctional curable material and a total weight of the at least
one hydrophilic multifunctional curable material ranges from 1:1 to
10:1.
[0033] According to some of any of the embodiments described
herein, a total amount of the at least one monofunctional curable
material ranges from 1 to 10, or from 3 to 10, or from 5 to 10, %
by weight, of the total weight of the formulation.
[0034] According to some of any of the embodiments described
herein, a total amount of the at least one hydrophilic
multifunctional curable material ranges from 1 to 5, % by weight,
of the total weight of the formulation.
[0035] According to some of any of the embodiments described
herein, the at least one hydrophilic multifunctional curable
material provides, when hardened per se, a material that is water
insoluble.
[0036] According to some of any of the embodiments described
herein, at least one of the monofunctional curable material(s)
comprises a hydrophilic monofunctional curable material.
[0037] According to some of any of the embodiments described
herein, at least one of the monofunctional curable material(s)
comprises a hydroxyalkyl and/or an alkylene glycol moiety.
[0038] According to some of any of the embodiments described
herein, at least one of the hydrophilic multifunctional curable
material(s) comprises one or more alkylene glycol moieties.
[0039] According to some of any of the embodiments described
herein, the at least one non-curable material is a water-soluble or
water-miscible material.
[0040] According to some of any of the embodiments described
herein, the at least one non-curable material comprises a polymeric
material.
[0041] According to some of any of the embodiments described
herein, the at least one non-curable material further comprises a
non-polymeric material.
[0042] According to some of any of the embodiments described
herein, a weight ratio of a total weight of the at least one
polymeric non-curable material and a total weight of the at least
one non-polymeric non-curable material ranges from 2:1 to 1:2.
[0043] According to some of any of the embodiments described
herein, the formulation comprises: the at least one monofunctional
curable material, in an amount of from 3 to 10, % by weight; the at
least one multifunctional curable material in an amount of from 3
to 5, % by weight; at least one polymeric non-curable material in
an amount of from 30 to 60, % by weight; and at least one
non-polymeric non-curable material in an amount of from 30 to 60, %
by weight, wherein a total amount of the non-curable materials is
at least 80% by weight.
[0044] According to some of any of the embodiments described
herein, the formulation is devoid of water.
[0045] According to some of any of the embodiments described
herein, the formulation features a viscosity of from 8 to 40
centipoises at 75.degree. C., as measured using a Brookfield
viscometer.
[0046] According to some of any of the embodiments described
herein, the additive manufacturing is 3D inkjet printing.
[0047] According to some of any of the embodiments described
herein, the formulation features, when hardened, Young's modulus of
from 10 to 100, or from 10 to 80 kPa.
[0048] According to some of any of the embodiments described
herein, the formulation features, when hardened, a gel material
that is flowable upon application of positive pressure.
[0049] According to some of any of the embodiments described
herein, the pressure ranges from 0.1 to 1.5 bars, or from 0.2 to
1.2 bars, or from 0.2 to 1 bar.
[0050] According to some of any of the embodiments described
herein, each of the curable materials is a UV-curable material.
[0051] According to some of any of the embodiments described
herein, each of the curable materials is an acrylic material.
[0052] According to some of any of the embodiments described
herein, the formulation further comprises a photoinitiator.
[0053] According to some of any of the embodiments described
herein, an amount of the photoinitiator is no more than 2% by
weight of the total weight of the formulation.
[0054] According to an aspect of some embodiments of the present
invention there is provided a method of additive manufacturing of a
three-dimensional object, the method comprising sequentially
forming a plurality of layers in a configured pattern corresponding
to the shape of the object, thereby forming the object,
[0055] wherein the formation of at least a few of the layers
comprises:
[0056] dispensing at least two building material formulations, the
at least two building material formulations comprise a modeling
material formulation M which, upon exposure to a curing condition,
forms a hardened modeling material M, and an FG formulation
according to any of the respective embodiments described herein,
which, upon exposure to the curing condition, forms a hardened
support material FG.
[0057] According to some of any of the embodiments described
herein, the dispensing is such that the hardened modeling material
M forms at least one hollow structure, and the material FG is at
least partially enclosed in the hollow structure.
[0058] According to some of any of the embodiments described
herein, the hollow structure is selected from a tubular structure,
a branched tubular structure, and a plurality of tubular structures
entangled with one another.
[0059] According to some of any of the embodiments described
herein, a diameter of at least one of the tubular structures is
less than 1 cm.
[0060] According to some of any of the embodiments described
herein, the material FG is completely enclosed in the hollow
structure.
[0061] According to an aspect of some embodiments of the present
invention there is provided a method of additive manufacturing of a
three-dimensional object having a cavity, the method comprising
sequentially forming a plurality of layers in a configured pattern
corresponding to a combined shape of the object and a sacrificial
object, in a manner that the sacrificial object is enclosed in by a
sacrificial shell, and the sacrificial shell is enclosed in the
cavity; and
[0062] removing the sacrificial object and the sacrificial shell
from the cavity;
[0063] wherein the sacrificial object comprises a modeling material
M, and the sacrificial shell is made of a support material FG
formed of the FG formulation as described herein in any of the
respective embodiments.
[0064] According to some of any of the embodiments described
herein, the sacrificial object also comprises the FG material, the
FG material being reinforced by the modeling material M.
[0065] According to some of any of the embodiments described
herein, the modeling material M occupies from about 60% to about
80% of a volume of the sacrificial object.
[0066] Unless otherwise defined, all technical and/or scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which the invention pertains.
Although methods and materials similar or equivalent to those
described herein can be used in the practice or testing of
embodiments of the invention, exemplary methods and/or materials
are described below. In case of conflict, the patent specification,
including definitions, will control. In addition, the materials,
methods, and examples are illustrative only and are not intended to
be necessarily limiting.
[0067] Implementation of the method and/or system of embodiments of
the invention can involve performing or completing selected tasks
manually, automatically, or a combination thereof. Moreover,
according to actual instrumentation and equipment of embodiments of
the method and/or system of the invention, several selected tasks
could be implemented by hardware, by software or by firmware or by
a combination thereof using an operating system.
[0068] For example, hardware for performing selected tasks
according to embodiments of the invention could be implemented as a
chip or a circuit. As software, selected tasks according to
embodiments of the invention could be implemented as a plurality of
software instructions being executed by a computer using any
suitable operating system. In an exemplary embodiment of the
invention, one or more tasks according to exemplary embodiments of
method and/or system as described herein are performed by a data
processor, such as a computing platform for executing a plurality
of instructions. Optionally, the data processor includes a volatile
memory for storing instructions and/or data and/or a non-volatile
storage, for example, a magnetic hard-disk and/or removable media,
for storing instructions and/or data. Optionally, a network
connection is provided as well. A display and/or a user input
device such as a keyboard or mouse are optionally provided as
well.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0069] Some embodiments of the invention are herein described, by
way of example only, with reference to the accompanying drawings.
With specific reference now to the drawings in detail, it is
stressed that the particulars shown are by way of example and for
purposes of illustrative discussion of embodiments of the
invention. In this regard, the description taken with the drawings
makes apparent to those skilled in the art how embodiments of the
invention may be practiced.
[0070] In the drawings:
[0071] FIGS. 1A-1D are schematic illustrations of an additive
manufacturing system according to some embodiments of the
invention;
[0072] FIGS. 2A-2C are schematic illustrations of printing heads
according to some embodiments of the present invention;
[0073] FIGS. 3A and 3B are schematic illustrations demonstrating
coordinate transformations according to some embodiments of the
present invention;
[0074] FIG. 4 is a flowchart diagram of a method suitable for AM of
a three-dimensional object according to various exemplary
embodiments of the present invention;
[0075] FIGS. 5A-C present photographs of an object printed with a
DM core made of an exemplary FG formulation and a grid of an
Agilus.TM. modeling formulation M and a coating made of Agilus.TM.
as material M (about 1 mm) (FIG. 5A), and of the same object upon
immersing it a 2% NaOH solution (FIG. 5B) and upon complete
dissolution of the hardened material FG (FIG. 5C).
[0076] FIGS. 6A and 6B present schematic illustrations of digital
material modes that can be performed in additive manufacturing
methods employing exemplary formulations according to some of the
present embodiments;
[0077] FIGS. 7A-C present schematic presentations of a "dog bone"
model fabricated in experiments performed according to some
embodiments of the present invention.
[0078] FIG. 8 presents comparative plots showing the tear
resistance of dog bone models prepared while employing an
Agilus.TM. formulation as the modeling formulation M and exemplary
FG formulations according to the present embodiments, SUP706 or a
liquid formulation L, as the support material formulation.
[0079] FIGS. 9, 10 and 11 present series of photographs presenting
the removal of an FG material according to some of the present
embodiments from models having hollow structures.
[0080] FIGS. 12A and 12B are schematic illustrations of a tubular
structure according to some embodiments of the present
invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION
[0081] The present invention, in some embodiments thereof, relates
to additive manufacturing and, more particularly, but not
exclusively, to curable formulations which provide, when hardened,
materials featuring properties of a weak gel, and to additive
manufacturing of three-dimensional objects using same.
[0082] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not
necessarily limited in its application to the details of
construction and the arrangement of the components and/or methods
set forth in the following description and/or illustrated in the
drawings and/or the Examples. The invention is capable of other
embodiments or of being practiced or carried out in various
ways.
[0083] The present inventors have realized that while practicing
currently known additive manufacturing processes for fabricating
three-dimensional objects, difficulties are observed in the
formation and cleaning of parts that have intricate geometries, for
example, geometries that contain hollow structures, such as
cavities, enclosed volumes, thin and/or entangled and/or branched
hollow tubular structures (e.g., pipes, tunnels), and sponge-like
structures, which feature a narrow opening or are completely
enclosed. Non-limiting exemplary objects featuring such intricate
geometries are objects featuring structures of bodily organs such
as a blood vessel, inner parts of a bone, and a heart.
[0084] More specifically, the present inventors have realized that
when fabricating such objects, using, for example, 3D-inkjet
printing, intricate parts of the object such as cavities, enclosed
volumes, entangled and branched tubes, pipes and/or tunnel systems,
are typically filled with a support material, typically a material
featuring properties of a gel, whereby removal of the support
material upon object fabrication via conventional mechanical and/or
chemical techniques is difficult to perform, inefficient and
time-consuming, and moreover, causes damage to the intricate parts
and/or the entire object.
[0085] Mechanical techniques for support material removal, such as
water jet and compressed air, are inefficient in case of enclosed
or partially enclosed hollow structures since the physical
accessibility of the jet to the support material is limited, and
the applied pressure required for complete removal of the support
material may damage the object. Chemical techniques for support
material removal, which involve dissolution of the support material
upon contacting a cleaning solution, are inefficient in case of
enclosed or partially enclosed hollow structures since it requires
diffusion of the cleaning solution to these portions of the
object.
[0086] As discussed hereinabove, currently practiced support
material formulations typically include curable and non-curable
materials, which, when hardened, form gel or gel-like materials.
Herein and in the art, the term "gel" describes a material, often
referred to as a semi-solid material, which comprises a
three-dimensional solid network, typically made of fibrous
structures chemically or physically linked therebetween, and a
liquid phase encaged within this network. Gels are typically
characterized by a consistency of a solid (e.g., are non-fluidic),
and feature relatively low Tensile strength, relatively low Shear
Modulus, e.g., lower than 100 kPa, and a Shear Loss Modulus to
Shear Storage modulus (tan delta, G''/G') value lower than 1. Gels
can be characterized as flowable when subjected to a positive
pressure of at least 0.5 bar, preferably at least 1 bar, or higher,
or, alternatively, as non-flowable when subjected to a pressure
lower than 1 bar or lower than 0.5 bar or of 0.3 bar or lower.
[0087] Gel-like materials according to the present embodiments are
typically soft materials, which can be gels or solids, which
feature mechanical and rheological properties of a gel, as
described herein.
[0088] Currently practiced support material formulations typically
comprise a mixture of curable and non-curable materials, and, when
hardened, form hardened support materials which are also referred
to herein as gel-like support material or as gel support material
(e.g., Material S).
[0089] Most of the currently practiced hardened support materials
are typically water miscible, or water-dispersible or
water-soluble, as defined herein.
[0090] PCT International Patent Application Publication Nos. WO
2019/021291, WO 2019/021292 and WO 2019/021295, all by the present
Assignee, describe formulations that are usable in additive
manufacturing of three-dimensional objects, and which provide, upon
exposure to a curing condition, a liquid or liquid-like
material.
[0091] The present inventors have conceived utilizing curable
formulations that form a weak gel material upon exposure to a
curing condition.
[0092] Herein and in the art, the term "gel" describes a material,
often referred to as a semi-solid material, which comprises a
three-dimensional solid network, typically made of fibrous
structures chemically or physically linked therebetween, and a
liquid phase encaged within this network. Gels are typically
characterized by a consistency of a solid (e.g., are non-fluidic),
and feature relatively low Tensile strength, relatively low Shear
Modulus, e.g., lower than 100 kPa, and a Shear Loss Modulus to
Shear Storage modulus (tan delta, G''/G') value lower than 1. Gels
are typically characterized as being flowable when subjected to a
positive pressure of at least 0.5 bar, preferably at least 1 bar,
or higher, and as being non-flowable when subject to a pressure
lower than 1 bar or lower than 0.5 bar or of 0.3 bar or lower.
[0093] Gel-like materials are typically soft materials, which can
be gels or solids, which feature mechanical and rheological
properties of a gel. By "weak gel" it is meant a material featuring
a gel consistency at room temperature and a Shear modulus at the
middle to lower range of gels, that is, lower than 80 kPa, or lower
than 50 kPa or lower.
[0094] The present inventors have devised formulations that provide
such weak gels, which further exhibit flowability when subjected to
a relatively low pressure, for example, in a range of from 0.1 bar
to 1.5 bars, or from 0.2 bar to 1.5 bar, or from 0.1 bar to 1.2
bars, or from 0.2 bar to 1.2 bars, or from 0.2 bar to 1 bar, or
from 0.5 bar to 1.5 bars, or from 0.5 bar to 1 bar, or from 0.1 bar
to 0.8 bar, or from 0.2 bar to 0.8 bar, or from 0.5 bar to 0.8 bar,
or from 0.1 bar to 0.5 bar, or from 0.2 bar to 0.5 bar, including
any intermediate values and subranges therebetween. Such
formulations are also referred to herein as FG formulations or
formulations FG or as flowing gel formulations. The material formed
when these formulations are hardened is referred to herein as
Material FG or an FG material or as flowing gel material or as
flowing gel hardened material.
[0095] Herein throughout, the term "printed object" or "fabricated
object" describes a product of the additive manufacturing process.
This term refers to the product obtained by a method as described
herein, before removal of the support material (e.g., the FG
material optionally in combination with a support material S). A
printed object is therefore made of hardened (e.g., cured) modeling
material and hardened (e.g., cured) support material.
[0096] The term "printed object" as used herein throughout refers
to a whole printed object or a part thereof.
[0097] The terms "model object", "final object", "object" and
"model", as used herein, describe a final product of the
manufacturing process. This term refers to the product obtained by
a method as described herein, after removal of the support
material(s). The model therefore essentially consists of a hardened
(solidified, cured) modeling material, unless otherwise
indicated.
[0098] The terms "model", "model object", "final object" and
"object", as used herein throughout, refer to a whole object or a
part thereof.
[0099] By "hollow structure" in an object it is meant that the
object comprises one or more parts that have cavities (non-solid
portions) therein. The cavity can be completely or partially
enclosed by the solid material. When partially enclosed, the cavity
can feature a narrow opening (e.g., less than 10 mm in diameter) to
the outermost surface of the object. The cavities can be of any
shape, for example, tubular, spherical, cylindrical, cuboidal,
pyramidal, and of more complexed shapes, such as, but not limited
to, non-simply connected shape, including, for example, entangled
and/or branched shapes (e.g., entangled and/or branched tunnels
and/or pipes).
[0100] In some embodiments, the cavity has at least one dimension
at the millimeter scale, that is, from 0.1 mm to 10 mm, or from 0.1
mm to 8 mm, or from 0.1 mm to 5 mm, or from 1 mm to 5 mm.
[0101] Exemplary hollow structures include, but are not limited to,
thin tubular structures, such as tubes, pipes and tunnels, which
can be branched and/or entangled, and which have in at least a
portion thereof a diameter at the millimeter scale, as defined
herein.
[0102] In some embodiments, the cavity is fully-enclosed, that is,
it is an inner hollow structure within the object that is not
exposed to an environment surrounding the object. Such an inner
hollow structure can be of any shape/geometry, as described herein,
and its dimensions can range from a millimeter scale, as defined
herein, to a few centimeters (e.g., 1-20, or 1-10, or 1-5 cm) and
up to 30, 40, 50 cm and even more.
[0103] Exemplary such objects include, but are not limited to,
sealed bottles, cups, and any other sealed receptacle.
[0104] Embodiments of the present invention relate to a novel
formulation which provides a flowing gel (FG) material as defined
herein, and to systems and methods employing these formulations in
additive manufacturing of a three-dimensional object as described
herein. The method and system of the present embodiments
manufacture three-dimensional objects based on computer object data
in a layerwise manner by forming a plurality of layers in a
configured pattern corresponding to the shape of the objects. The
computer object data can be in any known format, including, without
limitation, a Standard Tessellation Language (STL) or a
StereoLithography Contour (SLC) format, Virtual Reality Modeling
Language (VRML), Additive Manufacturing File (AMF) format, Drawing
Exchange Format (DXF), Polygon File Format (PLY) or any other
format suitable for Computer-Aided Design (CAD).
[0105] Each layer is formed by additive manufacturing apparatus
which scans a two-dimensional surface and patterns it. While
scanning, the apparatus visits a plurality of target locations on
the two-dimensional layer or surface, and decides, for each target
location or a group of target locations, whether or not the target
location or group of target locations is to be occupied by building
material formulation, and which type of building material
formulation is to be delivered thereto. The decision is made
according to a computer image of the surface.
[0106] In preferred embodiments of the present invention the AM
comprises three-dimensional printing, more preferably
three-dimensional inkjet printing. In these embodiments a building
material formulation is dispensed from a dispensing head having one
or more nozzles arrays to deposit building material formulation in
layers on a supporting structure. The AM apparatus thus dispenses
building material formulation in target locations which are to be
occupied and leaves other target locations void. The apparatus
typically includes a plurality of dispensing heads, each of which
can be configured to dispense a different building material
formulation from the or different nozzle array. Thus, different
target locations can be occupied by different building material
formulations.
[0107] Herein throughout, some embodiments of the present invention
are described in the context of the additive manufacturing being a
3D inkjet printing. However, other additive manufacturing
processes, such as, but not limited to, SLA and DLP, as described
in further detail hereinbelow, are contemplated.
[0108] An uncured building material can comprise one or more
modeling material formulations, and can be dispensed such that
different parts of the object are made, upon curing, of different
cured modeling formulations or different combinations thereof, and
hence are made of different cured modeling materials or different
mixtures of cured modeling materials.
[0109] The formulations forming the building material (modeling
material formulations and optionally support material formulations)
comprise one or more curable materials, which, when exposed to a
curing condition (e.g., curing energy), form hardened (e.g., cured,
solidified) material.
[0110] Herein throughout, a "curable material" is a compound
(typically a monomeric or oligomeric compound, yet optionally a
polymeric material) which, when exposed to a curing condition
(e.g., curing energy), as described herein, solidifies or hardens
to form a cured material. Curable materials are typically
polymerizable materials, which undergo polymerization and/or
cross-linking when exposed to suitable curing condition, typically
a source of energy. A curable material, according to the present
embodiments, can harden or solidify (cure) while being exposed to a
curing condition which can be a curing energy, and/or to another
curing condition such as contact with a chemical reagent or
exposure to the environment.
[0111] The terms "curable" and "solidifiable" as used herein are
interchangeable.
[0112] According to some embodiments of the present invention, a
curable material as described herein hardens upon undergoing
polymerization, and is also referred to herein as a polymerizable
material.
[0113] The polymerization can be, for example, free-radical
polymerization, cationic polymerization or anionic polymerization,
and each can be induced when exposed to curing energy such as, for
example, radiation, heat, etc., as described herein, or to a curing
condition other than curing energy.
[0114] In some of any of the embodiments described herein, a
curable material is a photopolymerizable material, which
polymerizes and/or undergoes cross-linking upon exposure to
radiation, as described herein, and in some embodiments the curable
material is a UV-curable material, which polymerizes and/or
undergoes cross-linking upon exposure to UV or UV-vis radiation, as
described herein.
[0115] In some embodiments, a curable material as described herein
is a photopolymerizable material that polymerizes via photo-induced
free-radical polymerization. Alternatively, the curable material is
a photopolymerizable material that polymerizes via photo-induced
cationic polymerization.
[0116] In some of any of the embodiments described herein, a
curable material can be a monomer, an oligomer or a short-chain
polymer, each being polymerizable and/or cross-linkable as
described herein.
[0117] In some of any of the embodiments described herein, when a
curable material is exposed to a curing condition (e.g.,
radiation), it hardens (solidifies, cures) by any one, or
combination, of chain elongation and cross-linking.
[0118] In some of any of the embodiments described herein, a
curable material is a monomer or a mixture of monomers which can
form a polymeric material upon a polymerization reaction, when
exposed to a curing condition (e.g., curing energy) at which the
polymerization reaction occurs. Such curable materials are also
referred to herein as monomeric curable materials.
[0119] In some of any of the embodiments described herein, a
curable material is an oligomer or a mixture of oligomers which can
form a polymeric material upon a polymerization reaction, when
exposed to a curing condition (e.g., curing energy) at which the
polymerization reaction occurs. Such curable materials are also
referred to herein as oligomeric curable materials.
[0120] In some of any of the embodiments described herein, a
curable material, whether monomeric or oligomeric, can be a
mono-functional curable material or a multi-functional curable
material.
[0121] Herein, a mono-functional curable material comprises one
functional group that can undergo polymerization when exposed to a
curing condition such as curing energy (e.g., radiation).
[0122] A multi-functional curable material comprises two or more,
e.g., 2, 3, 4 or more, functional groups that can undergo
polymerization when exposed to curing energy. Multi-functional
curable materials can be, for example, di-functional,
tri-functional or tetra-functional curable materials, which
comprise 2, 3 or 4 groups that can undergo polymerization,
respectively. The two or more functional groups in a
multi-functional curable material are typically linked to one
another by a linking moiety, as defined herein. When the linking
moiety is an oligomeric or polymeric moiety, the multi-functional
group is an oligomeric or polymeric multi-functional curable
material. Multi-functional curable materials can undergo
polymerization when subjected to curing energy and/or act as
cross-linkers.
[0123] The final three-dimensional object is made of the modeling
material formulation or a combination of modeling material
formulations or modeling and support material formulations or
modification thereof (e.g., following curing). All these operations
are well-known to those skilled in the art of solid freeform
fabrication.
[0124] In some exemplary embodiments of the invention an object is
manufactured by dispensing two or more different building material
formulations, each formulation from a different dispensing head of
the AM. The building material formulations are optionally and
preferably deposited in layers during the same pass of the printing
heads. The formulations and combination of formulations within the
layer are selected according to the desired properties of the
object.
[0125] Herein throughout, the phrase "uncured building material" or
"building material formulation" collectively describes the
materials that are dispensed during the fabrication process so as
to sequentially form the layers, as described herein. This phrase
encompasses uncured materials (also referred to herein as building
material formulation(s)) dispensed so as to form the printed
object, namely, one or more uncured modeling material
formulation(s), and uncured materials dispensed so as to form the
support, namely uncured support material formulations.
[0126] The types of building material formulations can be
categorized into two major categories: modeling material
formulation and support material formulation. The support material
formulation can serve as a supporting matrix or construction for
supporting the object or object parts during the fabrication
process and/or other purposes, e.g., providing hollow or porous
objects. Support constructions may additionally include modeling
material formulation elements, e.g. for further support strength. A
building material formulation that provides a liquid or liquid-like
material upon exposure to a curing condition can also be
categorized, according to some embodiments of the present invention
as a support material formulation.
[0127] Herein throughout, the phrases "cured modeling material" and
"hardened modeling material" or simply "modeling material", which
are used interchangeably, describe the part of the building
material that forms a model object, as defined herein, upon
exposing the dispensed building material to curing, and following
removal of the support material. The cured or hardened modeling
material can be a single hardened material or a mixture of two or
more hardened materials, depending on the modeling material
formulations used in the method, as described herein. A building
material formulation that provides a liquid or liquid-like material
upon exposure to a curing condition can also be categorized,
according to some embodiments of the present invention as a
modeling material formulation.
[0128] Herein throughout, the phrase "modeling material
formulation", which is also referred to herein interchangeably as
"modeling formulation", describes a part of the uncured building
material which is dispensed so as to form the model object, as
described herein. The modeling formulation is an uncured modeling
formulation, which, upon exposure to a curing condition, forms the
final object or a part thereof.
[0129] An uncured building material can comprise one or more
modeling formulations, and can be dispensed such that different
parts of the model object are made upon curing different modeling
formulations, and hence are made of different cured modeling
materials or different mixtures of cured modeling materials.
[0130] Herein throughout, the phrase "hardened support material" is
also referred to herein interchangeably as "cured support material"
or simply as "support material" and describes the part of the
building material that is intended to support the fabricated final
object during the fabrication process, and which is removed once
the process is completed and a hardened modeling material is
obtained.
[0131] Herein throughout, the phrase "support material
formulation", which is also referred to herein interchangeably as
"support formulation" or simply as "formulation", describes a part
of the uncured building material which is dispensed so as to form
the support material, as described herein. The support material
formulation is an uncured formulation. When a support material
formulation is a curable formulation, it forms, upon exposure to a
curing condition, a hardened support material.
[0132] Support materials, which can be either liquid or liquid-like
materials or hardened, typically gel or gel-like materials, are
also referred to herein as sacrificial materials, which are
removable after layers are dispensed and exposed to a curing
energy, to thereby expose the shape of the final object.
[0133] Currently practiced support materials typically comprise a
mixture of curable and non-curable materials, and are also referred
to herein as gel-like support material or as gel support
material.
[0134] Currently practiced support materials are typically water
miscible, or water-dispersible or water-soluble.
[0135] Herein throughout, the term "water-miscible" describes a
material which is at least partially dissolvable or dispersible in
water, that is, at least 50% of the molecules move into the water
upon mixture at room temperature. This term encompasses the terms
"water-soluble" and "water dispersible".
[0136] Herein throughout, the term "water-soluble" describes a
material that when mixed with water in equal volumes or weights, at
room temperature, a homogeneous solution is formed.
[0137] Herein throughout, the term "water-dispersible" describes a
material that forms a homogeneous dispersion when mixed with water
in equal volumes or weights, at room temperature.
[0138] Herein throughout, the phrase "dissolution rate" describes a
rate at which a substance is dissolved in a liquid medium.
Dissolution rate can be determined, in the context of the present
embodiments, by the time needed to dissolve a certain amount of a
support material. The measured time is referred to herein as
"dissolution time".
[0139] Herein throughout, whenever the phrase "weight percents" is
indicated in the context of embodiments of a formulation (e.g., a
building material formulation), it is meant weight percents of the
total weight of the respective formulation.
[0140] The phrase "weight percents" is also referred to herein as
"% by weight" or "% wt."
[0141] The Flowing Gel Formulation:
[0142] According to an aspect of some embodiments of the present
invention there is provided a formulation that is usable as a
support material formulation in additive manufacturing of a
three-dimensional object. According to some embodiments of the
invention, the formulation provides, upon exposure to a curing
condition, a material that features properties of a weak gel, as
defined herein. According to some embodiments of the invention, the
formulation provides, upon exposure to a curing condition, a
material that features properties of a flowing or flowable gel, as
defined herein. The formulation is also referred to herein as
"flowing gel formulation" or "FG formulation" or "FLG formulation"
or "formulation FG".
[0143] According to embodiments of the present invention, the
formulation comprises: at least one monofunctional curable
material; at least one multifunctional curable material; and at
least one water-miscible non-curable material.
[0144] According to some of any of the embodiments described
herein, the formulation is devoid of water.
[0145] In some of any of the embodiments described herein, the
support material formulation is devoid of a silicon polyether.
[0146] By "devoid of" it is meant that an amount of the indicated
material (e.g., water) is no more than 2%, or no more than 1%, or
no more than 0.5%, or no more than 0.1%, or no more than 0.5%, or
no more than 0.1%, or no more than 0.05%, or no more than 0.01%, by
weight, and can be even less or null.
[0147] According to some of any of the embodiments described
herein, a total amount of the curable materials is 20% or less, by
weight, of the total weight of the formulation, and can be, for
example, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, % by weight,
or less, of the total weight of the formulation.
[0148] According to some of any of the embodiments described
herein, a weight ratio of a total weight of the monofunctional
curable material(s) and a total weight of the multifunctional
curable material(s) ranges from 1:1 to 10:1, including any
intermediate values and subranges therebetween, and can be, for
example, 1:1, or 1:2, or 1:3, or 1:4, or 1:5, or 1:6, or 1:7, or
1:9, or 1:9 or 1:10. According to some of any of the embodiments
described herein, a total amount of the one or more monofunctional
curable material(s) ranges from 1 to 10, or from 3 to 10, or from 5
to 10, % by weight, of the total weight of the formulation,
including any intermediate values and subranges therebetween.
[0149] According to some of any of the embodiments described
herein, a total amount of the one or more multifunctional curable
material(s) ranges from 1 to 5, % by weight, of the total weight of
the formulation.
[0150] According to some of any of the embodiments described
herein, one or more, or each, of the monofunctional curable
material(s) is a hydrophilic material, as defined herein.
[0151] According to some of any of the embodiments described
herein, one or more, or each, of the monofunctional curable
material(s) is a water-miscible or water-soluble material, as
defined herein.
[0152] Herein throughout, the term "hydrophilic" describes a
physical property of a compound or a portion of a compound (e.g., a
chemical group in a compound) which accounts for transient
formation of bond(s) with water molecules, typically through
hydrogen bonding.
[0153] A hydrophilic compound or portion of a compound (e.g., a
chemical group in a compound) is one that is typically
charge-polarized and capable of hydrogen bonding.
[0154] Hydrophilic compounds or groups typically include one or
more electron-donating heteroatoms which form strong hydrogen bonds
with water molecules. Such heteroatoms include, but are not limited
to, oxygen and nitrogen. Preferably, a ratio of the number of
carbon atoms to a number of heteroatoms in a hydrophilic compounds
or groups is 10:1 or lower, and can be, for example, 8:1, more
preferably 7:1, 6:1, 5:1 or 4:1, or lower. It is to be noted that
hydrophilicity of compounds and groups may result also from a ratio
between hydrophobic and hydrophilic moieties in the compound or
chemical group, and does not depend solely on the above-indicated
ratio.
[0155] Hydrophilic compounds dissolve more readily in water than in
oil or other hydrophobic solvents. Hydrophilic compounds can be
determined by, for example, as having Log P lower than 0.5, when
Log P is determined in octanol and water phases, at a temperature
lower than 50.degree. C., or lower than 40.degree. C., or lower
than 35.degree. C. or lower than 30.degree. C., e.g., at 25.degree.
C.
[0156] Alternatively, hydrophilic compounds can be determined by,
for example, the Hansen parameters, as having relative energy
distance (RED) higher than 1, when calculated for interaction with
water as a solvent, at a temperature lower than 50, or lower than
40.degree. C., or lower than 35.degree. C. or lower than 30.degree.
C., e.g., at 25.degree. C.
[0157] A hydrophilic compound can have one or more hydrophilic
groups that render the compound hydrophilic. Such groups are
typically polar groups, comprising one or more electron-donating
heteroatoms such as oxygen and nitrogen. The hydrophilic group can
be, for example, one or more substituent(s) of a monomeric
mono-functional curable material or two or more substituents or
interrupting groups of an oligomeric mono-functional curable
material. The hydrophilic group can be, for example, one or more
substituent(s) of a monomeric multi-functional curable material or
one or more substituents or interrupting groups of a linking moiety
of a monomeric multi-functional curable moiety. The hydrophilic
group can be, for example, two or more substituents or interrupting
groups of an oligomeric linking moiety in oligomeric
multi-functional curable material.
[0158] Exemplary hydrophilic groups include, but are not limited
to, an electron-donating heteroatom, a carboxylate, a
thiocarboxylate, oxo (.dbd.O), a linear amide, hydroxy, a
(C1-4)alkoxy, an (C1-4)alcohol, a heteroalicyclic (e.g., having a
ratio of carbon atoms to heteroatoms as defined herein), a cyclic
carboxylate such as lactone, a cyclic amide such as lactam, a
carbamate, a thiocarbamate, a cyanurate, an isocyanurate, a
thiocyanurate, urea, thiourea, an alkylene glycol (e.g., ethylene
glycol or propylene glycol), and a hydrophilic polymeric or
oligomeric moiety, as these terms are defined hereinunder, and any
combinations thereof (e.g., a hydrophilic group that comprises two
or more of the indicated hydrophilic groups).
[0159] In some embodiments, the hydrophilic group is, or comprises,
an electron donating heteroatom, a carboxylate, a heteroalicyclic,
an alkylene glycol and/or a hydrophilic oligomeric moiety.
[0160] A hydrophilic polymeric or oligomeric moiety, as used
herein, comprises a polymeric chain which comprises hydrophilic
groups as defined herein. The hydrophilic groups can be heteroatoms
within the backbone chain of the polymeric moiety, as, for example,
in poly(alkylene glycols) or hydrophilic pendant groups. A
polymeric or oligomeric moiety, according to some embodiments of
the present invention, preferably has from 10 to 40 repeating
backbone units, more preferably from 10 to 20 repeating backbone
units.
[0161] A hydrophilic mono-functional curable material according to
some embodiments of the present invention can be a vinyl-containing
compound represented by Formula I:
##STR00001##
[0162] wherein at least one of R.sub.1 and R.sub.2 is and/or
comprises a hydrophilic group, as defined herein.
[0163] The (.dbd.CH.sub.2) group in Formula I represents a
polymerizable group, and is typically a UV-curable group, such that
the material is a UV-curable material.
[0164] For example, R.sub.1 is a hydrophilic group as defined
herein and R.sub.2 is a non-hydrophilic group, for example,
hydrogen, C(1-4) alkyl, C(1-4) alkoxy, or any other substituent, as
long as the compound is hydrophilic, as defined herein.
[0165] In some embodiments, R.sub.1 is a carboxylate,
--C(.dbd.O)--OR' group, and R.sub.2 is hydrogen, and the compound
is a mono-functional acrylate monomer. In some of these
embodiments, R.sub.2 is methyl, and the compound is mono-functional
methacrylate monomer. In other embodiments, R.sub.2 is a
hydrophilic substituent, namely, a substituent which is, or which
comprises, a hydrophilic group as described herein.
[0166] In some of any of these embodiments, the carboxylate group,
--C(.dbd.O)--OR', comprises R' which is a hydrophilic group.
Exemplary R' groups include, but are not limited to,
heteroalicyclic groups (having a ratio of 5:1 or lower of carbon
atoms to electron-donating heteroatoms, such as morpholine,
tetrahydrofurane, oxalidine, and the likes), hydroxyl,
C(1-4)alkoxy, thiol, alkylene glycol or a polymeric or oligomeric
moiety, as described herein. An exemplary monomeric mono-functional
acrylate is acryloyl morpholine (ACMO).
[0167] In some embodiments, R.sub.1 is amide, and in some
embodiments, it is a cyclic amide such as lactam, and the compound
is a vinyl lactam. In some embodiments, R.sub.1 is a cyclic
carboxylate such as lactone, and the compound is a vinyl
lactone.
[0168] When one or both of R.sub.1 and R.sub.2 comprise a polymeric
or oligomeric moiety, for example, a hydrophilic oligomeric moiety,
as defined herein, the mono-functional curable compound of Formula
I is an exemplary oligomeric mono-functional curable material.
Otherwise, it is an exemplary monomeric mono-functional curable
material.
[0169] Exemplary oligomeric mono-functional curable materials
include, but are not limited to, a mono-(meth)acrylated urethane
oligomer derivative of polyethylene glycol, a mono-(meth)acrylated
polyol oligomer, a mono-(meth)acrylated oligomer having hydrophilic
substituents, and a mono-(meth)acrylated polyethylene glycol (e.g.,
methoxypolyethylene glycol). (Meth)acrylated means that the
oligomer or polymer comprises an acrylate or methacrylate
functional group.
[0170] In some embodiments, R.sub.1 is a carboxylate and R' is a
poly(alkylene glycol), as defined herein. An exemplary such
hydrophilic monofunctional curable material is hexa(ethylene
glycol) acrylate, (6-PEA).
[0171] In some embodiments, R.sub.1 is a hydrophilic
heteroalicyclic group, as defined herein. An exemplary such
hydrophilic monofunctional curable material is ACMO.
[0172] In some embodiments, in case there are two or more
monofunctional curable materials, all of the monofunctional curable
materials are hydrophilic and/or water-soluble or water-miscible
materials, and in some embodiments, only one of these materials is
a hydrophilic and/or water-soluble or water-miscible material.
[0173] In some embodiments, one or more of the monofunctional
curable materials provides, when hardened per se, a material that
is water-soluble. An exemplary such material is ACMO.
[0174] In some embodiments, each of the monofunctional curable
materials provides, when hardened per se, a material that is
water-soluble.
[0175] In some embodiments, one or more of the monofunctional
curable materials provides, when hardened per se, a material that
is water-insoluble. Exemplary such materials include PEA6 and
HEAA.
[0176] In some embodiments, each of the monofunctional curable
materials provides, when hardened per se, a material that is
water-insoluble.
[0177] In some embodiments, one or more of the monofunctional
curable materials provides, when hardened per se, a material that
is water-soluble, and one or more of the monofunctional curable
materials provides, when hardened per se, a material that is
water-insoluble.
[0178] In some of any of the embodiments described herein, at least
one of the monofunctional curable material(s) is a curable material
that comprises a hydroxyalkyl (e.g., HEAA) and/or an alkylene
glycol moiety (e.g., a poly(alkylene glycol acrylate such as, for
example, PEA6).
[0179] According to some of any of the embodiments described
herein, each of the one or more multifunctional curable materials
is a hydrophilic material.
[0180] A hydrophilic multi-functional curable material according to
some embodiments of the present invention can be represented by
Formula II:
##STR00002##
[0181] wherein:
[0182] each of R.sub.3, R.sub.4 and R.sub.5 is independently
hydrogen, C(1-4)alkyl, or a hydrophilic group, as defined
herein;
[0183] each of L.sub.1, L.sub.2 and L.sub.3 is independently a
linking moiety or absent;
[0184] each of P.sub.1 and P.sub.2 is independently a hydrophilic
group as defined herein or absent;
[0185] each of X.sub.1, X.sub.2 and X.sub.3 is independently
C(1-4)alkyl, or a hydrophilic group, as defined herein, or absent;
and
[0186] each of n, m and k is 0, 1, 2, 3 or 4, provided that n+m+k
is at least 2, and provided that at least one of R.sub.3, R.sub.4,
R.sub.5, X.sub.1, X.sub.2, X.sub.3 P.sub.1 and P.sub.2 is a
hydrophilic group, as defined herein.
[0187] Multi-functional curable materials of Formula II in which
one, two or all of X.sub.1, X.sub.2 and X.sub.3, when present, is
oxo, are multi-functional acrylates, which can be further
substituted by a hydrophilic group, as described hereinabove. When
one or more of R.sub.3, R.sub.4 and R.sub.5, when present, is
methyl, the curable materials are multi-functional
methacrylates.
[0188] Multifunctional curable materials in which one, two or all
of X.sub.1, X.sub.2 and X.sub.3, when present, is oxo, can include
a combination of acrylate and methacrylate functional moieties.
[0189] In some embodiments, the acrylate or methacrylate
multifunctional curable material is monomeric, such that none of
P.sub.1 and P.sub.2 is a polymeric or oligomeric moiety. In some of
these embodiments, one or both of P.sub.1 and P.sub.2 is a
hydrophilic group as described herein, for example, an alkylene
glycol, or any other hydrophilic linking group, or a short chain
(e.g., of 1-6 carbon atoms), substituted or unsubstituted
hydrocarbon moiety, as defined herein.
[0190] In some embodiments, one or both of P.sub.1 and P.sub.2 is a
polymeric or oligomeric moiety as defined herein, and the curable
compound is an oligomeric multi-functional curable material, for
example, an oligomeric multi-functional acrylate or methacrylate,
as described herein for X.sub.1, X.sub.2 and/or X.sub.3. If both
P.sub.1 and P.sub.2 are present, L.sub.2 can be, for example, a
linking moiety such as a hydrocarbon, comprising alkyl, cycloalkyl,
aryl and any combination thereof. Exemplary such curable materials
include ethoxylated or methoxylated polyethylene glycol diacrylate,
and ethoxylated bisphenol A diacrylate.
[0191] Other non-limiting examples include polyethylene glycol
diacrylate, polyethylene glycol dimethacrylate, polyethylene
glycol-polyethylene glycol urethane diacrylate, and a partially
acrylated polyol oligomer.
[0192] In some embodiments, one or more of P.sub.1 and P.sub.2 is,
or comprises, a poly(alkylene glycol) moiety, as defined
herein.
[0193] In some of any of the embodiments of an acrylate or
methacrylate multifunctional curable material of Formula II, one or
more of R.sub.3, R.sub.4 and R.sub.5 is a hydrophilic group as
described, for example, for R.sub.1 and R.sub.2 in Formula I,
herein. In these embodiments, P.sub.1 and/or P.sub.2 can be present
or absent, and can be, or comprise, a hydrophilic group or not, as
long as the material is hydrophilic, as defined herein.
[0194] Alternatively, one, two or all of X.sub.1, X.sub.2 and
X.sub.3, when present, can be --O--, such that at least one
functional moiety in the multi-functional curable material is vinyl
ether.
[0195] In some embodiments, n and m are each 1, k is 0, X.sub.1 is
O, X.sub.2 is absent, and the compound is a vinyl ether, which can
be substituted or not. In some of these embodiments, L.sub.1,
L.sub.2, L.sub.3, P.sub.1 and P.sub.2 are absent, and the compound
is a monomeric vinyl ether. Examples of monomeric vinyl ethers
include ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl
ether, cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether, butyl
vinyl ether, ethyleneglycol monovinyl ether, diethyleneglycol
divinyl ether, butane diol divinyl ether, hexane diol divinyl
ether, cyclohexane dimethanol monovinyl ether and the like.
[0196] In some embodiments, P.sub.1 and P.sub.2 are absent, and one
of L.sub.1 and L.sub.2 is an alkylene chain substituted by one or
more hydrophilic groups. An exemplary such curable compound is
1,4-cyclohexane dimethanol divinyl ether.
[0197] In some embodiments, one or more of P.sub.1 and P.sub.2 is a
hydrophilic polymeric or oligomeric moiety, as defined herein. In
some embodiments, one or more of P.sub.1 and P.sub.2 is, or
comprises, a poly(alkylene glycol) moiety, as defined herein. In
some embodiments the polymeric moiety is substituted by one or more
vinyl ether substituents.
[0198] In some of any of the embodiments related to Formula II, one
or more of the substituents of the polymerizable group, R.sub.3,
R.sub.4 and R.sub.5, can be a hydrophilic group as described for
R.sub.1 and R.sub.2 in Formula I herein.
[0199] In some of any of the embodiments related to Formula II,
when P.sub.1 and P.sub.2 is a polymeric or oligomeric moiety, this
moiety can comprise hydrophilic heteroatoms as defined herein,
within the backbone chain or the backbone chain can be substituted
by hydrophilic groups, as described herein.
[0200] In some of any of the embodiments described herein, one or
more, or each of the multifunctional curable materials is a
hydrophilic material as defined herein.
[0201] In some of any of the embodiments described herein, one or
more, or each of the multifunctional curable materials is a
water-soluble or water-miscible material as defined herein.
[0202] In some of any of the embodiments described herein, one or
more, or each of the multifunctional curable materials provides,
when hardened, a material that is water-insoluble.
[0203] In some of any of the embodiments described herein, one or
more, or each, of the multifunctional curable material(s) comprises
one or more alkylene glycol moieties. In some of these embodiments,
a multifunctional curable material comprises a poly(alkylene
glycol) moiety.
[0204] In some of any of the embodiments described herein, one or
more, or each, of the multifunctional curable material(s) is a
di-functional material.
[0205] In some of any of the embodiments described herein, the
multifunctional curable material(s) comprise or is a poly(alkylene
glycol)diacrylate. The poly(alkylene glycol)diacrylate can be of
from 20 to 1000 alkylene glycol units, including any intermediate
values and subranges therebetween.
[0206] In an exemplary embodiment, the multifunctional curable
material(s) comprises or is a poly(ethylene glycol)diacrylate, of
from 20 to 1000, or from 100 to 1000, or from 200 to 1000, or from
100 to 800, or from 200 to 800, or from 400 to 800, ethylene glycol
units, including any intermediate values and subranges
therebetween.
[0207] The formulation as described herein further comprises
non-curable materials. In some embodiments, a total amount of the
non-curable materials is at least 70%, or at least 75 5, or at
least 80%, or at least 85%, by weight, of the total weight of the
formulation.
[0208] The term "non-curable" encompasses materials that are
non-polymerizable under any conditions or materials that are
non-curable under conditions at which the mono-functional and
multifunctional curable materials as described herein are curable,
or under any condition used in a fabrication of an object according
to the present embodiments. Such materials are typically devoid of
a polymerizable group or of a UV-photopolymerizable group. In some
embodiments, the material is non-reactive towards the curable
material as described herein, that is, it does not react with the
curable material and is incapable of interfering with the curing of
the curable materials, under the fabrication conditions, including
the curing conditions.
[0209] In some of any of the embodiments described herein the
non-curable material is water soluble or water dispersible or water
miscible material, as defined herein.
[0210] In some of any of the embodiments described herein, one or
more, or each, of the non-curable material(s) is a water-miscible
or water-soluble material.
[0211] In some of any of the embodiments described herein, one or
more of the non-curable materials is a polymeric material, for
example, a water-miscible or water-soluble polymeric material.
[0212] In some embodiments, the non-curable material is a polymeric
material which comprises a plurality of hydrophilic groups as
defined herein, either within the backbone chain of the polymer or
as pendant groups. Exemplary such polymeric materials are polyols.
Some representative examples include, but are not limited to,
Polyol 3165, polypropylene glycol, polyethylene glycol,
polyglycerol, polyglyme, ethoxylated forms of these polymers,
paraffin oil and the like, and any combination thereof.
[0213] In exemplary embodiments, the non-curable polymeric material
comprises poly(ethylene glycol) and/or polyol 3165. The polymeric
materials can be of any molecular weight.
[0214] In some embodiments, the one or more polymeric materials and
an amount thereof are selected such that the formulation features a
viscosity that is suitable for the additive manufacturing method,
as described herein.
[0215] In some of any of the embodiments described herein, a
polymeric material has a MW of at least 500, or at least 600
grams/mol.
[0216] In some of any of the embodiments described herein, a
polymeric material has a MW of no more than 3000, or nor more than
2500, or no more than 2000 or no more than 1500, grams/mol.
[0217] In some of any of the embodiments described herein, a
polymeric material has a MW of from about 500 to about 2500
grams/mol, including any intermediate value and subranges
therebetween.
[0218] In some of any of the embodiments described herein, the one
or more non-curable material(s) comprise a non-polymeric material,
for example, a water-soluble or water-miscible non-polymeric
material.
[0219] Exemplary such non-curable, non-polymeric material, include,
but are not limited to, propane diol (e.g., 1,2-propandoil, also
referred to herein and in the art as propylene glycol), propane
triol, glycerol, butyl diglyme (Butyl Di Glycol Acetate, Diethylene
glycol butyl ether acetate,2-(2-Butoxyethoxy)ethyl acetate),
Diethylene glycol monobutyl ether (BDG), (EDGAc) Diethylene glycol
monoethyl ether acetate (EDGAc; DGMEA), Di(ethylene glycol) ethyl
ether (DEGEE), Tri(propyleneglycol)methyl ether, Dipropylene glycol
monomethyl ether (DPGME), Di(propylene glycol) methyl ether acetate
(DPGMEA), propylene carbonate (1,2-Propanediol cyclic carbonate,
4-Methyl-1,3-dioxolan-2-one), Diethylene glycol methyl ether
(DGME), Diethylene glycol methyl ether (TGMME),
1-Methoxy-2-propanol (PGME/PM; Propyleneglycol monomethyl ether),
and Propylene glycol monomethyl ether acetate (PGMEA).
[0220] In some of any of the embodiments described herein, the
formulation comprises a water-miscible, non-curable material which
comprises a mixture of two or more of the polymeric and
non-polymeric water-miscible, non-curable materials described
herein. An exemplary such a mixture may comprise two or more of a
poly(ethylene glycol), a propane diol, glycerol and a polyol such
as Polyol 3165.
[0221] In some of these embodiments, a weight ratio of a total
weight of the one or more polymeric non-curable material(s) and a
total weight of the one or more non-polymeric non-curable
material(s) ranges from 2:1 to 1:2, including any intermediate
values and subranges therebetween.
[0222] An exemplary, non-limiting, formulation according to the
present embodiments comprises: One or more monofunctional curable
material(s), as described herein in any of the respective
embodiments, in an amount of from 3 to 10, % by weight; One or more
hydrophilic multifunctional (e.g., di-functional) curable
material(s), as described herein in any of the respective
embodiments, in an amount of from 3 to 5, % by weight;
[0223] One or more polymeric non-curable material(s), as described
herein in any of the respective embodiments, in an amount of from
30 to 60, % by weight; and
[0224] One or more non-polymeric non-curable material(s), as
described herein in any of the respective embodiments, in an amount
of from 30 to 60, % by weight, and a total amount of the
non-curable materials is at least 80% by weight of the total weight
of the formulation.
[0225] In some of any of the embodiments described herein, the
formulation is usable in additive manufacturing such as 3D inkjet
printing.
[0226] In some of any of the embodiments described herein, the
formulation features properties (e.g., viscosity, surface tension,
jettability) that are suitable for additive manufacturing such as
3D inkjet printing, as described herein.
[0227] In some embodiments, the formulation features a viscosity of
from 8 to 40, or from 8 to 30, or from 8 to 25, centipoises at the
jetting temperature (e.g., at 75.degree. C.).
[0228] In some of any of the embodiments described herein, and as
discussed hereinabove, the formulation provides, when hardened, a
material that features properties of weak gel.
[0229] In some of any of the embodiments described herein, and as
discussed hereinabove, the formulation provides, when hardened, a
material that features an elastic modulus (e.g., Young's modulus)
of from 10 to 100, or from 10 to 80, or from 20 to 80, or from 10
to 50, or from 20 to 50, or from 10 to 70, or from 20 to 70, or
from 30 to 80, or from 30 to 70, or from 30 to 100, or from 20 to
90, or from 10 to 90, or from 30 to 90, or from 40 to 90, or from
40 to 100, or from 40 to 80, or from 40 to 70, or from 20 to 60, or
from 10 to 60, or from 30 to 60, or from 40 to 60, or from 50 to
100, or from 50 to 90, or from 50 to 80, or from 50 to 70, or from
50 to 60, kPa, including any intermediate values and subranges
therebetween.
[0230] According to some of any of the embodiments described
herein, the formulation provides, when hardened, a gel material
that is flowable upon application of positive pressure, as
described herein.
[0231] According to some of these embodiments, the positive
pressure is such that is applied by pressing the formulation by a
human being.
[0232] In some of any of the embodiments described herein, one or
more, and preferably each, of the monofunctional and
multifunctional curable materials is a UV-curable material.
[0233] In some of any of the embodiments described herein, one or
more, and preferably each, of the monofunctional and
multifunctional curable materials is an acrylic material, as
defined herein.
[0234] In some of any of the embodiments described herein, the
formulation further comprises one or more photoinitiator(s).
[0235] In some of these embodiments, a total amount of the
photoinitiator is no more than 2% by weight of the total weight of
the formulation, and can be, for example, in a range of from 0.1 to
2%, or from 0.1 to 1.5%, or from 0.5 to 1.5%, by weight, including
any intermediate values and subranges therebetween.
[0236] The photoinitiator can be a free radical photo-initiator, a
cationic photo-initiator, or any combination thereof.
[0237] A free radical photoinitiator may be any compound that
produces a free radical upon exposure to radiation such as
ultraviolet or visible radiation and thereby initiates a
polymerization reaction. Non-limiting examples of suitable
photoinitiators include phenyl ketones, such as alkyl/cycloalkyl
phenyl ketones, benzophenones (aromatic ketones) such as
benzophenone, methyl benzophenone, Michler's ketone and xanthones;
acylphosphine oxide type photo-initiators such as
2,4,6-trimethylbenzolydiphenyl phosphine oxide (TMPO),
2,4,6-trimethylbenzoylethoxyphenyl phosphine oxide (TEPO), and
bisacylphosphine oxides (BAPO's); benzoins and benzoin alkyl ethers
such as benzoin, benzoin methyl ether and benzoin isopropyl ether
and the like. Examples of photoinitiators are alpha-amino ketone,
and 1-hydroxycyclohexyl phenyl ketone (e.g., marketed as
Irgacure.RTM. 184).
[0238] A free-radical photo-initiator may be used alone or in
combination with a co-initiator. Co-initiators are used with
initiators that need a second molecule to produce a radical that is
active in the UV-systems. Benzophenone is an example of a
photoinitiator that requires a second molecule, such as an amine,
to produce a curable radical. After absorbing radiation,
benzophenone reacts with a ternary amine by hydrogen abstraction,
to generate an alpha-amino radical which initiates polymerization
of acrylates. Non-limiting example of a class of co-initiators are
alkanolamines such as triethylamine, methyldiethanolamine and
triethanolamine.
[0239] Suitable cationic photoinitiators include, for example,
compounds which form aprotic acids or Bronsted acids upon exposure
to ultraviolet and/or visible light sufficient to initiate
polymerization. The photoinitiator used may be a single compound, a
mixture of two or more active compounds, or a combination of two or
more different compounds, i.e. co-initiators. Non-limiting examples
of suitable cationic photoinitiators include aryldiazonium salts,
diaryliodonium salts, triarylsulphonium salts, triarylselenonium
salts and the like. An exemplary cationic photoinitiator is a
mixture of triarylsolfonium hexafluoroantimonate salts.
[0240] In some of any of the embodiments described herein, the
formulation may further comprise one or more additional agents that
are beneficially used in the fabrication process. Such agents
include, for example, surface active agents, inhibitors and
stabilizers.
[0241] In some embodiments, a support material formulation as
described herein comprises a surface active agent. A surface-active
agent may be used to reduce the surface tension of the formulation
to the value required for jetting or for other printing process,
which is typically around 30 dyne/cm. An exemplary such agent is a
silicone surface additive such as, but not limited to, surface
active agents marketed as the BYK family.
[0242] In some embodiments, a support material formulation as
described herein further comprises an inhibitor, which inhibits
pre-polymerization of the curable material during the fabrication
process and before it is subjected to curing conditions. An
exemplary stabilizer (inhibitor) is
Tris(N-nitroso-N-phenylhydroxylamine) Aluminum Salt (NPAL) (e.g.,
as marketed under FirstCure.RTM. NPAL).
[0243] Suitable stabilizers include, for example, thermal
stabilizers, which stabilize the formulation at high
temperatures.
[0244] Model Fabrication:
[0245] According to an aspect of some embodiments of the present
invention there is provided a method of fabricating a
three-dimensional model object, which utilizes a formulation as
described herein as support material formulation. The method is
also referred to herein as a fabrication process or as a model
fabrication process. In some embodiments, the method comprises
dispensing an uncured building material so as to sequentially form
a plurality of layers in a configured pattern corresponding to the
shape of the object. In some embodiments, the (uncured) building
material comprises one or more modeling material formulation(s) and
one or more support material formulation(s), and one or more of the
support material formulations is a formulation as described herein
in any of the respective embodiments.
[0246] The modeling material formulation can be any modeling
material formulation usable in additive manufacturing such as 3D
inkjet printing, and is preferably curable under the same
conditions at which the support material formulation is
curable.
[0247] According to some embodiments of the present invention, the
fabrication method is additive manufacturing of a three-dimensional
model object.
[0248] According to some embodiments of this aspect, formation of
each layer is effected by dispensing at least one uncured building
material, and exposing the dispensed building material to curing
energy or curing conditions, to thereby form a cured building
material, which is comprised of a cured modeling material and a
cured support material.
[0249] According to some of any of the embodiments described
herein, the additive manufacturing is preferably by
three-dimensional inkjet printing.
[0250] The method of the present embodiments manufactures
three-dimensional objects in a layerwise manner by forming a
plurality of layers in a configured pattern corresponding to the
shape of the objects.
[0251] Each layer is formed by an additive manufacturing apparatus
which scans a two-dimensional surface and patterns it. While
scanning, the apparatus visits a plurality of target locations on
the two-dimensional layer or surface, and decides, for each target
location or a group of target locations, whether or not the target
location or group of target locations is to be occupied by building
material, and which type of building material (e.g., a modeling
material formulation or a support material formulation) is to be
delivered thereto. The decision is made according to a computer
image of the surface.
[0252] When the AM is by three-dimensional printing, an uncured
building material, as defined herein, is dispensed from a
dispensing head having a set of nozzles to deposit building
material in layers on a supporting structure. The AM apparatus thus
dispenses building material in target locations which are to be
occupied and leaves other target locations void. The apparatus
typically includes a plurality of dispensing heads, each of which
can be configured to dispense a different building material. Thus,
different target locations can be occupied by different building
materials (e.g., a modeling formulation and/or a support
formulation, as defined herein).
[0253] A representative and non-limiting example of a system 110
suitable for AM of an object 112 according to some embodiments of
the present invention is illustrated in FIG. 1A. System 110
comprises an additive manufacturing apparatus 114 having a
dispensing unit 16 which comprises a plurality of dispensing heads.
Each head preferably comprises one or more arrays of nozzles 122,
as illustrated in FIGS. 2A-C described below, through which a
liquid building material 124 is dispensed.
[0254] According to some embodiments of the present invention,
apparatus 114 operates at a temperature that does not exceed
35.degree. C.
[0255] Preferably, but not obligatorily, apparatus 114 is a
three-dimensional inkjet printing apparatus, in which case the
dispensing heads are printing heads, and the building material is
dispensed via inkjet technology from a printing head having one or
more arrays of nozzles to deposit building material formulation in
layers on a supporting structure. This need not necessarily be the
case, since, for some applications, it may not be necessary for the
additive manufacturing apparatus to employ three-dimensional
printing techniques. Representative examples of additive
manufacturing apparatus contemplated according to various exemplary
embodiments of the present invention include, without limitation,
fused deposition modeling apparatus and fused material deposition
apparatus.
[0256] The term "printing head" as used herein represents a
dispensing head usable in 3D printing such as 3D inkjet
printing.
[0257] The term "dispensing head" encompasses the term "printing
head" in the context of embodiments relating to 3D inkjet
printing.
[0258] Each dispensing head is optionally and preferably fed via
one or more building material formulation reservoirs which may
optionally include a temperature control unit (e.g., a temperature
sensor and/or a heating device), and a material formulation level
sensor. To dispense a building material formulation, a voltage
signal is applied to the dispensing heads to selectively deposit
droplets of a selected formulation or a selected combination of two
or more formulations via the dispensing head nozzles, for example,
as in piezoelectric inkjet printing technology. Another example
includes thermal inkjet printing heads. In these types of heads,
there are heater elements in thermal contact with the building
material formulation, for heating the building material formulation
to form gas bubbles therein, upon activation of the heater elements
by a voltage signal.
[0259] The gas bubbles generate pressures in the building material
formulation, causing droplets of building material formulation to
be ejected through the nozzles. Piezoelectric and thermal printing
heads are known to those skilled in the art of solid freeform
fabrication. For any types of inkjet dispensing heads, the
dispensing rate of the head depends on the number of nozzles, the
type of nozzles and the applied voltage signal rate
(frequency).
[0260] Preferably, but not obligatorily, the overall number of
dispensing nozzles or nozzle arrays is selected such that half of
the dispensing nozzles are designated to dispense support material
and half of the dispensing nozzles are designated to dispense
modeling material, i.e. the number of nozzles jetting modeling
materials is the same as the number of nozzles jetting support
material. In the representative example of FIG. 1A, four dispensing
heads 16a, 16b, 16c and 16d are illustrated. Each of heads 16a,
16b, 16c and 16d has a nozzle array. In this Example, heads 16a and
16b can be designated for modeling material/s and heads 16c and 16d
can be designated for support material. Thus, head 16a can dispense
a first modeling material, head 16b can dispense a second modeling
material and heads 16c and 16d can both dispense support material.
In an alternative embodiment, heads 16c and 16d, for example, may
be combined in a single head having two nozzle arrays for
depositing support material. In a further alternative embodiment
any one or more of the printing heads may have more than one nozzle
arrays for depositing more than one material formulation, e.g. two
nozzle arrays for depositing two different modeling material
formulations or a modeling material formulation and a support
material formulation, each formulation via a different array or
number of nozzles.
[0261] Yet it is to be understood that it is not intended to limit
the scope of the present invention and that the number of modeling
material printing heads (modeling heads) and the number of support
material printing heads (support heads) may differ. Generally, the
number of arrays of nozzles that dispense modeling material
formulation, the number of arrays of nozzles that dispense support
material formulation, and the number of nozzles in each respective
array are selected such as to provide a predetermined ratio, a,
between the maximal dispensing rate of the support material
formulation and the maximal dispensing rate of modeling material
formulation. The value of the predetermined ratio, a, is preferably
selected to ensure that in each formed layer, the height of
modeling material equals the height of support material. Typical
values for a are from about 0.6 to about 1.5.
[0262] For example, for a=1, the overall dispensing rate of support
material is generally the same as the overall dispensing rate of
the modeling material when all the arrays of nozzles operate.
[0263] For example, apparatus 114 can comprise M modeling heads
each having m arrays of p nozzles, and S support heads each having
s arrays of q nozzles such that
M.times.m.times.p=S.times.s.times.q. Each of the M.times.m modeling
arrays and S.times.s support arrays can be manufactured as a
separate physical unit, which can be assembled and disassembled
from the group of arrays. In this embodiment, each such array
optionally and preferably comprises a temperature control unit and
a material formulation level sensor of its own, and receives an
individually controlled voltage for its operation.
[0264] In some embodiments, the temperature control unit of at
least a few of the arrays is configured so as not to exceed
45.degree. C., or 40.degree. C., or 35.degree. C.
[0265] Apparatus 114 can further comprise a hardening device 324
which can include any device configured to emit light, heat or the
like that may cause the deposited material to harden. For example,
hardening device 324 can comprise one or more radiation sources,
which can be, for example, an ultraviolet or visible or infrared
lamp, or other sources of electromagnetic radiation, or electron
beam source, depending on the modeling material being used. In some
embodiments of the present invention, hardening device 324 serves
for curing or solidifying the modeling material.
[0266] As used herein, the term "dispensing head" or "depositing
head" encompass printing heads which are dispensing heads usable in
3D printing such as 3D inkjet printing.
[0267] The dispensing head(s) and radiation source are preferably
mounted in a frame or block 128 which is preferably operative to
reciprocally move over a tray 360, which serves as the working
surface. In some embodiments of the present invention the radiation
sources are mounted in the block such that they follow in the wake
of the dispensing heads to at least partially cure or solidify the
materials just dispensed by the dispensing heads. Tray 360 is
positioned horizontally. According to the common conventions an
X-Y-Z Cartesian coordinate system is selected such that the X-Y
plane is parallel to tray 360. Tray 360 is preferably configured to
move vertically (along the Z direction), typically downward. In
various exemplary embodiments of the invention, apparatus 114
further comprises one or more leveling devices 132, e.g. a roller
326. Leveling device 326 serves to straighten, level and/or
establish a thickness of the newly formed layer prior to the
formation of the successive layer thereon. Leveling device 326
preferably comprises a waste collection device 136 for collecting
the excess material generated during leveling. Waste collection
device 136 may comprise any mechanism that delivers the material to
a waste tank or waste cartridge.
[0268] In use, the dispensing heads of unit 16 move in a scanning
direction, which is referred to herein as the X direction, and
selectively dispense building material in a predetermined
configuration in the course of their passage over tray 360. The
building material typically comprises one or more types of support
material and one or more types of modeling material. The passage of
the dispensing heads of unit 16 is followed by the curing of the
modeling material(s) by radiation source 126. In the reverse
passage of the heads, back to their starting point for the layer
just deposited, an additional dispensing of building material may
be carried out, according to predetermined configuration. In the
forward and/or reverse passages of the dispensing heads, the layer
thus formed may be straightened by leveling device 326, which
preferably follows the path of the dispensing heads in their
forward and/or reverse movement. Once the dispensing heads return
to their starting point along the X direction, they may move to
another position along an indexing direction, referred to herein as
the Y direction, and continue to build the same layer by reciprocal
movement along the X direction. Alternately, the dispensing heads
may move in the Y direction between forward and reverse movements
or after more than one forward-reverse movement. The series of
scans performed by the dispensing heads to complete a single layer
is referred to herein as a single scan cycle.
[0269] Once the layer is completed, tray 360 is lowered in the Z
direction to a predetermined Z level, according to the desired
thickness of the layer subsequently to be printed. The procedure is
repeated to form three-dimensional object 112 in a layerwise
manner.
[0270] In another embodiment, tray 360 may be displaced in the Z
direction between forward and reverse passages of the dispensing
head of unit 16, within the layer. Such Z displacement is carried
out in order to cause contact of the leveling device with the
surface in one direction and prevent contact in the other
direction.
[0271] System 110 optionally and preferably comprises a building
material supply system 330 which comprises the building material
containers or cartridges and supplies a plurality of building
materials to fabrication apparatus 114.
[0272] A control unit 152 controls fabrication (e.g., printing)
apparatus 114 and optionally and preferably also supply system 330.
Control unit 152 typically includes an electronic circuit
configured to perform the controlling operations. Control unit 152
preferably communicates with a data processor 154 which transmits
digital data pertaining to fabrication instructions based on
computer object data, e.g., a CAD configuration represented on a
computer readable medium in a form of a Standard Tessellation
Language (STL) format or the like. Typically, control unit 152
controls the voltage applied to each dispensing head or nozzle
array and the temperature of the building material in the
respective printing head or respective nozzle array, as described
herein.
[0273] According to some embodiments of the present invention,
control unit 152 is operated such that the temperature of the
building material (uncured) does not exceed 40.degree. C. or
35.degree. C. Once the manufacturing data is loaded to control unit
152 it can operate without user intervention. In some embodiments,
control unit 152 receives additional input from the operator, e.g.,
using data processor 154 or using a user interface 116
communicating with unit 152. User interface 116 can be of any type
known in the art, such as, but not limited to, a keyboard, a touch
screen and the like. For example, control unit 152 can receive, as
additional input, one or more building material types and/or
attributes, such as, but not limited to, color, characteristic
distortion and/or transition temperature, viscosity, electrical
property, magnetic property. Other attributes and groups of
attributes are also contemplated.
[0274] Another representative and non-limiting example of a system
10 suitable for AM of an object according to some embodiments of
the present invention is illustrated in FIGS. 1B-D. FIGS. 1B-D
illustrate a top view (FIG. 1B), a side view (FIG. 1C) and an
isometric view (FIG. 1D) of system 10.
[0275] In the present embodiments, system 10 comprises a tray 12
and a plurality of inkjet printing heads 16, each having each
having one or more arrays of nozzles with respective one or more
pluralities of separated nozzles. Tray 12 can have a shape of a
disk or it can be annular. Non-round shapes are also contemplated,
provided they can be rotated about a vertical axis. Printing heads
16 can be any of the printing heads described above with respect to
system 110.
[0276] Tray 12 and heads 16 are optionally and preferably mounted
such as to allow a relative rotary motion between tray 12 and heads
16. This can be achieved by (i) configuring tray 12 to rotate about
a vertical axis 14 relative to heads 16, (ii) configuring heads 16
to rotate about vertical axis 14 relative to tray 12, or (iii)
configuring both tray 12 and heads 16 to rotate about vertical axis
14 but at different rotation velocities (e.g., rotation at opposite
direction). While the embodiments below are described with a
particular emphasis to configuration (i) wherein the tray is a
rotary tray that is configured to rotate about vertical axis 14
relative to heads 16, it is to be understood that the present
application contemplates also configurations (ii) and (iii). Any
one of the embodiments described herein can be adjusted to be
applicable to any of configurations (ii) and (iii), and one of
ordinary skills in the art, provided with the details described
herein, would know how to make such adjustment.
[0277] In the following description, a direction parallel to tray
12 and pointing outwardly from axis 14 is referred to as the radial
direction r, a direction parallel to tray 12 and perpendicular to
the radial direction r is referred to herein as the azimuthal
direction .phi., and a direction perpendicular to tray 12 is
referred to herein is the vertical direction z.
[0278] The radial direction r in system 10 enacts the indexing
direction y in system 110, and the azimuthal direction .phi. enacts
the scanning direction x in system 110. Therefore, the radial
direction is interchangeable referred to herein as the indexing
direction, and the azimuthal direction is interchangeable referred
to herein as the scanning direction.
[0279] The term "radial position," as used herein, refers to a
position on or above tray 12 at a specific distance from axis 14.
When the term is used in connection to a printing head, the term
refers to a position of the head which is at specific distance from
axis 14. When the term is used in connection to a point on tray 12,
the term corresponds to any point that belongs to a locus of points
that is a circle whose radius is the specific distance from axis 14
and whose center is at axis 14.
[0280] The term "azimuthal position," as used herein, refers to a
position on or above tray 12 at a specific azimuthal angle relative
to a predetermined reference point. Thus, radial position refers to
any point that belongs to a locus of points that is a straight line
forming the specific azimuthal angle relative to the reference
point.
[0281] The term "vertical position," as used herein, refers to a
position over a plane that intersect the vertical axis 14 at a
specific point.
[0282] Tray 12 serves as a supporting structure for
three-dimensional printing. The working area on which one or
objects are printed is typically, but not necessarily, smaller than
the total area of tray 12. In some embodiments of the present
invention the working area is annular. The working area is shown at
26. In some embodiments of the present invention tray 12 rotates
continuously in the same direction throughout the formation of
object, and in some embodiments of the present invention tray
reverses the direction of rotation at least once (e.g., in an
oscillatory manner) during the formation of the object. Tray 12 is
optionally and preferably removable. Removing tray 12 can be for
maintenance of system 10, or, if desired, for replacing the tray
before printing a new object.
[0283] In some embodiments of the present invention system 10 is
provided with one or more different replacement trays (e.g., a kit
of replacement trays), wherein two or more trays are designated for
different types of objects (e.g., different weights) different
operation modes (e.g., different rotation speeds), etc. The
replacement of tray 12 can be manual or automatic, as desired. When
automatic replacement is employed, system 10 comprises a tray
replacement device 36 configured for removing tray 12 from its
position below heads 16 and replacing it by a replacement tray (not
shown). In the representative illustration of FIG. 1B tray
replacement device 36 is illustrated as a drive 38 with a movable
arm 40 configured to pull tray 12, but other types of tray
replacement devices are also contemplated.
[0284] Exemplified embodiments for the printing head 16 are
illustrated in FIGS. 2A-C. These embodiments can be employed for
any of the AM systems described above, including, without
limitation, system 110 and system 10.
[0285] FIGS. 2A-B illustrate a printing head 16 with one (FIG. 2A)
and two (FIG. 2B) nozzle arrays 22. The nozzles in the array are
preferably aligned linearly, along a straight line. In embodiments
in which a particular printing head has two or more linear nozzle
arrays, the nozzle arrays are optionally and preferably can be
parallel to each other. When a printing head has two or more arrays
of nozzles (e.g., FIG. 2B) all arrays of the head can be fed with
the same building material formulation, or at least two arrays of
the same head can be fed with different building material
formulations.
[0286] When a system similar to system 110 is employed, all
printing heads 16 are optionally and preferably oriented along the
indexing direction with their positions along the scanning
direction being offset to one another.
[0287] When a system similar to system 10 is employed, all printing
heads 16 are optionally and preferably oriented radially (parallel
to the radial direction) with their azimuthal positions being
offset to one another. Thus, in these embodiments, the nozzle
arrays of different printing heads are not parallel to each other
but are rather at an angle to each other, which angle being
approximately equal to the azimuthal offset between the respective
heads. For example, one head can be oriented radially and
positioned at azimuthal position .phi..sub.1, and another head can
be oriented radially and positioned at azimuthal position
.phi..sub.2. In this example, the azimuthal offset between the two
heads is .phi..sub.1-.PHI..sub.2, and the angle between the linear
nozzle arrays of the two heads is also .phi..sub.1-.phi..sub.2.
[0288] In some embodiments, two or more printing heads can be
assembled to a block of printing heads, in which case the printing
heads of the block are typically parallel to each other. A block
including several inkjet printing heads 16a, 16b, 16c is
illustrated in FIG. 2C.
[0289] In some embodiments, system 10 comprises a support structure
30 positioned below heads 16 such that tray 12 is between support
structure 30 and heads 16. Support structure 30 may serve for
preventing or reducing vibrations of tray 12 that may occur while
inkjet printing heads 16 operate. In configurations in which
printing heads 16 rotate about axis 14, support structure 30
preferably also rotates such that support structure 30 is always
directly below heads 16 (with tray 12 between heads 16 and tray
12).
[0290] Tray 12 and/or printing heads 16 is optionally and
preferably configured to move along the vertical direction z,
parallel to vertical axis 14 so as to vary the vertical distance
between tray 12 and printing heads 16. In configurations in which
the vertical distance is varied by moving tray 12 along the
vertical direction, support structure 30 preferably also moves
vertically together with tray 12. In configurations in which the
vertical distance is varied by heads 16 along the vertical
direction, while maintaining the vertical position of tray 12
fixed, support structure 30 is also maintained at a fixed vertical
position.
[0291] The vertical motion can be established by a vertical drive
28. Once a layer is completed, the vertical distance between tray
12 and heads 16 can be increased (e.g., tray 12 is lowered relative
to heads 16) by a predetermined vertical step, according to the
desired thickness of the layer subsequently to be printed. The
procedure is repeated to form a three-dimensional object in a
layerwise manner.
[0292] The operation of inkjet printing heads 16 and optionally and
preferably also of one or more other components of system 10, e.g.,
the motion of tray 12, are controlled by a controller 20. The
controller can have an electronic circuit and a non-volatile memory
medium readable by the circuit, wherein the memory medium stores
program instructions which, when read by the circuit, cause the
circuit to perform control operations as further detailed
below.
[0293] Controller 20 can also communicate with a host computer 24
which transmits digital data pertaining to fabrication instructions
based on computer object data, e.g., in a form of a Standard
Tessellation Language (STL) or a StereoLithography Contour (SLC)
format, Virtual Reality Modeling Language (VRML), Additive
Manufacturing File (AMF) format, Drawing Exchange Format (DXF),
Polygon File Format (PLY) or any other format suitable for
Computer-Aided Design (CAD). The object data formats are typically
structured according to a Cartesian system of coordinates. In these
cases, computer 24 preferably executes a procedure for transforming
the coordinates of each slice in the computer object data from a
Cartesian system of coordinates into a polar system of coordinates.
Computer 24 optionally and preferably transmits the fabrication
instructions in terms of the transformed system of coordinates.
Alternatively, computer 24 can transmit the fabrication
instructions in terms of the original system of coordinates as
provided by the computer object data, in which case the
transformation of coordinates is executed by the circuit of
controller 20.
[0294] The transformation of coordinates allows three-dimensional
printing over a rotating tray. In non-rotary systems with a
stationary tray with the printing heads typically reciprocally move
above the stationary tray along straight lines. In such systems,
the printing resolution is the same at any point over the tray,
provided the dispensing rates of the heads are uniform. In system
10, unlike non-rotary systems, not all the nozzles of the head
points cover the same distance over tray 12 during at the same
time. The transformation of coordinates is optionally and
preferably executed so as to ensure equal amounts of excess
material at different radial positions. Representative examples of
coordinate transformations according to some embodiments of the
present invention are provided in FIGS. 3A-B, showing three slices
of an object (each slice corresponds to fabrication instructions of
a different layer of the objects), where FIG. 3A illustrates a
slice in a Cartesian system of coordinates and FIG. 3B illustrates
the same slice following an application of a transformation of
coordinates procedure to the respective slice.
[0295] Typically, controller 20 controls the voltage applied to the
respective component of the system 10 based on the fabrication
instructions and based on the stored program instructions as
described below.
[0296] Generally, controller 20 controls printing heads 16 to
dispense, during the rotation of tray 12, droplets of building
material in layers, such as to print a three-dimensional object on
tray 12. System 10 optionally and preferably comprises one or more
radiation sources 18, which can be, for example, an ultraviolet or
visible or infrared lamp, or other sources of electromagnetic
radiation, or electron beam source, depending on the modeling
material being used. Radiation source can include any type of
radiation emitting device, including, without limitation, light
emitting diode (LED), digital light processing (DLP) system,
resistive lamp and the like. Radiation source 18 serves for curing
or solidifying the modeling material. In various exemplary
embodiments of the invention the operation of radiation source 18
is controlled by controller 20 which may activate and deactivate
radiation source 18 and may optionally also control the amount of
radiation generated by radiation source 18.
[0297] In some embodiments of the invention, system 10 further
comprises one or more leveling devices 32 which can be manufactured
as a roller or a blade. Leveling device 32 serves to straighten the
newly formed layer prior to the formation of the successive layer
thereon. In some embodiments, leveling device 32 has the shape of a
conical roller positioned such that its symmetry axis 34 is tilted
relative to the surface of tray 12 and its surface is parallel to
the surface of the tray. This embodiment is illustrated in the side
view of system 10 (FIG. 2C).
[0298] The conical roller can have the shape of a cone or a conical
frustum.
[0299] The opening angle of the conical roller is preferably
selected such that there is a constant ratio between the radius of
the cone at any location along its axis 34 and the distance between
that location and axis 14. This embodiment allows roller 32 to
efficiently level the layers, since while the roller rotates, any
point p on the surface of the roller has a linear velocity which is
proportional (e.g., the same) to the linear velocity of the tray at
a point vertically beneath point p. In some embodiments, the roller
has a shape of a conical frustum having a height h, a radius
R.sub.1 at its closest distance from axis 14, and a radius R.sub.2
at its farthest distance from axis 14, wherein the parameters h,
R.sub.1 and R.sub.2 satisfy the relation R.sub.1/R.sub.2=(R-h)/h
and wherein R is the farthest distance of the roller from axis 14
(for example, R can be the radius of tray 12).
[0300] The operation of leveling device 32 is optionally and
preferably controlled by controller 20 which may activate and
deactivate leveling device 32 and may optionally also control its
position along a vertical direction (parallel to axis 14) and/or a
radial direction (parallel to tray 12 and pointing toward or away
from axis 14.
[0301] In some embodiments of the present invention printing heads
16 are configured to reciprocally move relative to tray along the
radial direction r. These embodiments are useful when the lengths
of the nozzle arrays 22 of heads 16 are shorter than the width
along the radial direction of the working area 26 on tray 12. The
motion of heads 16 along the radial direction is optionally and
preferably controlled by controller 20.
[0302] Some embodiments contemplate the fabrication of an object by
dispensing different materials from different arrays of nozzles
(belonging to the same or different printing head). These
embodiments provide, inter alia, the ability to select materials
from a given number of materials and define desired combinations of
the selected materials and their properties. According to the
present embodiments, the spatial locations of the deposition of
each material with the layer is defined, either to effect
occupation of different three-dimensional spatial locations by
different materials, or to effect occupation of substantially the
same three-dimensional location or adjacent three-dimensional
locations by two or more different materials so as to allow post
deposition spatial combination of the materials within the layer,
thereby to form a composite material at the respective location or
locations.
[0303] Any post deposition combination or mix of modeling materials
is contemplated. For example, once a certain material is dispensed
it may preserve its original properties. However, when it is
dispensed simultaneously with another modeling material or other
dispensed materials which are dispensed at the same or nearby
locations, a composite material having a different property or
properties to the dispensed materials is formed.
[0304] Further details on the principles and operations of an AM
system suitable for the present embodiments are found in U.S. Pat.
No. 9,031,680, and International Publication No. WO2016/009426, the
contents of which are hereby incorporated by reference.
[0305] The present embodiments thus enable the deposition of a
broad range of material combinations, and the fabrication of an
object which may consist of multiple different combinations of
materials, in different parts of the object, according to the
properties desired to characterize each part of the object.
[0306] FIG. 4 is a flowchart diagram of a method of additive
manufacturing of at least one tubular structure featuring
properties of a blood vessel, according to some embodiments of the
present invention. The method begins at 200 and optionally and
preferably proceeds to 201 at which 3D printing data in any of the
aforementioned computer object data formats are obtained.
[0307] The method can proceed to 202 at which droplets of one or
more uncured building material formulation(s) are dispensed to form
a layer. The building material formulation can be a modeling
material formulation such as, but not limited to, formulation M
providing hardened Material M when exposed to a curing condition as
described herein, and/or a support material formulation such as,
but not limited to, formulation FG providing hardened Material FG
when exposed to a curing condition, as described herein, and/or
formulation S providing hardened Material S when exposed to a
curing condition, as described herein, as described herein, and/or
formulation L providing hardened Material L when exposed to a
curing condition, as described herein.
[0308] The modeling material formulation is preferably dispensed in
a configured pattern corresponding to the shape of the object and
in accordance with the computer object data. The other building
material formulations are preferably dispensed in accordance with
the computer object data, but not necessarily in accordance with
the shape of the object, since these building material formulations
are typically sacrificial.
[0309] Optionally, before being dispensed, the uncured building
material, or a part thereof (e.g., one or more formulations of the
building material), is heated, prior to being dispensed. These
embodiments are particularly useful for uncured building material
formulations having relatively high viscosity at the operation
temperature of the working chamber of a 3D inkjet printing system.
The heating of the formulation(s) is preferably to a temperature
that allows jetting the respective formulation through a nozzle of
a printing head of a 3D inkjet printing system. In some embodiments
of the present invention, the heating is to a temperature at which
the respective formulation exhibits a viscosity of no more than X
centipoises, where X is about 30 centipoises, preferably about 25
centipoises and more preferably about 20 centipoises, or 18
centipoises, or 16 centipoises, or 14 centipoises, or 12
centipoises, or 10 centipoises, or even lower.
[0310] The heating can be executed before loading the respective
formulation into the printing head of the AM (e.g., 3D inkjet
printing) system, or while the formulation is in the printing head
or while the composition passes through the nozzle of the printing
head.
[0311] In some embodiments, the heating is executed before loading
of the respective formulation into the dispensing (e.g., inkjet
printing) head, so as to avoid clogging of the dispensing (e.g.,
inkjet printing) head by the formulation in case its viscosity is
too high.
[0312] In some embodiments, the heating is executed by heating the
dispensing (e.g., inkjet printing) heads, at least while passing
the modeling material formulation(s) through the nozzle of the
dispensing (e.g., inkjet printing) head.
[0313] In some embodiments, during the dispensing of at least one
of formulation FG and formulation L the operation of the cooling
system described below is temporarily terminated, so as to maintain
a still-air environment.
[0314] As used herein, "still-air environment" refers to an
environment in which there is no air flow, or in which an air flows
at speed less than 3 m/s.
[0315] At 203 the newly dispensed layer is straightened, for
example, using a leveling device 32 or 132, which is optionally and
preferably rotatable. When the newly dispensed layer contains
formulation FG and/or formulation L, the rotation speed of the
leveling device is preferably changed, typically reduced, relative
to its speed when straightening other layers. The control over the
rotation speed of the leveling device can be done by a controller
(e.g., controller 20 or controller 340).
[0316] The method optionally and preferably proceeds to 204 at
which the deposited layer is exposed to a curing condition (e.g.,
curing energy is applied), e.g., by means of a hardening device,
for example, a radiation source as described herein. Preferably,
the curing is applied to each individual layer following the
deposition of the layer and prior to the deposition of the previous
layer. Optionally, the deposited (dispensed) layers are exposed to
the curing condition other than a curing energy, such as, but not
limited to, contact with a chemical reagent or exposure to the
environment.
[0317] Operations 202-204, and in some embodiments also 201, are
preferably executed sequentially a plurality of times so that a
plurality of layers are sequentially dispensed and solidified. This
is illustrated in FIG. 4 as loop back arrows pointing from
operation 204 to operations 201 and 202. The layers are dispensed
to form a stack of model layers made of a modeling material
formulation, and a sacrificial structure, wherein the stack of
model layers and the sacrificial structure are separable from each
other in a manner that maintains the shape and size of the stack of
model layers without deformation. In various exemplary embodiments
of the invention operations 202-204 are executed to so that the
layers form an elongated core and a shell encapsulating the core,
wherein the core is optionally and preferably the sacrificial
structure as further detailed hereinunder. In some embodiments of
the present invention these operations are executed also to form an
intermediate shell between the core and the shell as further
detailed hereinunder. Each of the core, the shell and the
intermediate shell (when formed) is optionally and preferably
formed by dispensing a different building material formulation or a
different combination of building material formulations. The core
and the intermediate shell (when formed) are optionally and
preferably formed by dispensing a building material that can be
removed after the object is completed, and are therefore
sacrificial, as described herein.
[0318] In some embodiments of the present invention the method
dispenses digital material formulation for at least one of the
layers.
[0319] The phrase "digital material formulations", as used herein
and in the art, describes a combination of two or more material
formulations that are interlaced with each such that the printed
zones of a specific material formulation occupy a voxel, or few
voxels, or a voxel block, at least partially surrounded by a voxel,
or few voxels, or a voxel block of another material formulation.
Such digital material formulations may exhibit new properties that
are affected by the selection of types of material formulations
and/or the ratio and relative spatial distribution of two or more
material formulations.
[0320] In exemplary digital material formulations, the modeling or
support material formulation of each voxel or voxel block, obtained
upon curing, is independent of the modeling or support material
formulation of a neighboring voxel or voxel block, obtained upon
curing, such that each voxel or voxel block may result in a
different modeling or support material formulation and the new
properties of the whole object are a result of a spatial
combination, on the voxel level, of several different model
material formulations. In various exemplary embodiments of the
invention operations 202-204 are executed to form, for at least a
portion of layers, voxel elements containing different building
material formulations at interlaced locations.
[0321] As used herein, a "voxel" of a layer refers to a physical
three-dimensional elementary volume within the layer that
corresponds to a single pixel of a bitmap describing the layer. The
size of a voxel is approximately the size of a region that is
formed by a building material, once the building material is
dispensed at a location corresponding to the respective pixel,
leveled, and solidified.
[0322] Herein throughout, whenever the expression "at the voxel
level" is used in the context of a different material and/or
properties, it is meant to include differences between voxel
blocks, as well as differences between voxels or groups of few
voxels. In preferred embodiments, the properties of the whole part
are a result of a spatial combination, on the voxel block level, of
several different model materials.
[0323] In some embodiments, at least one, or at least a few (e.g.,
at least 10, at least 20, at least 30 at least 40, at least 50, at
least 60, at least 80, or more), of the layers is/are formed by
dispensing droplets of two or more building material formulations
at interlaced locations, each building material formulation from a
different nozzle array. These building material formulations can
include: (i) two or more modeling material formulations as
described herein in any of the respective embodiments, (ii) at
least one modeling material formulation and at least one support
material formulation as described herein in any of the respective
embodiments, or (iii) two or more support material formulations as
described herein in any of the respective embodiments.
[0324] In some embodiments, the method continues to 205, at which
the hardened material FG and/or material L or a digital material
containing one or more of hardened materials is removed from the
printed object, to thereby reveal the final object. The removal 205
can be in more than one way.
[0325] In some embodiments of the present invention the removal 205
is by application of pressure into a cavity or cavities filled by
these hardened materials. The pressure is optionally and preferably
sufficient to effect a flow of the hardened material FG or material
L out of the cavity without causing pressure induced damage to the
shell or shells enclosing the cavity. Optionally, and preferably in
case the liquid or liquid-like material features a thermal-thinning
behavior, the object is heated, for example, to a temperature of
from about 40.degree. C. to about 95.degree. C. prior to the
removal of the liquid or liquid-like material.
[0326] When the removal 205 is by application of pressure, the
pressure can be, for example, an air pressure, or a liquid
pressure, for example, in a form of a jet of an aqueous solution
(e.g., water).
[0327] The pressure is preferably no more than 1 bar, or no more
than 0.5, or no more than 0.3 bar, and can be, for example, 0.1
bar, 0.2 bar, or 0.3 bar.
[0328] Alternatively, and optionally in addition to the above, and
particularly in cases where the material to be removed is not
sufficiently flowable at ambient conditions, the removal 205 is
preceded by applying a condition that renders the material
flowable. Such conditions include, for example, application of
shear forces (for example, when the material to be removed is a
shear-thinning material), and/or application of heat (for example,
when the material to be removed is a thermo-thinning material).
[0329] Optionally and preferably, hardened support structures
(e.g., made of hardened material S) is also removed at 205. When
the hardened support structure forms the intermediate shell, its
removal is optionally and preferably by circulating in the cavity
occupied by the intermediate shell a solution capable of removing
the hardened support structure. For example, the hardened material
S can be water-soluble or water-miscible, in which case it can be
removed by contacting an aqueous solution at which it is
dissolvable or dispersible (e.g., a cleaning solution; an aqueous
solution that comprises an alkaline substance, at an amount of
about 1% to about 3% by weight of the solution).
[0330] In some embodiments of the present invention the hardened
support structure forms a pullable core surrounded by an
intermediate shell made of flowable material (e.g., hardened
material FG or material L), itself surrounded by a non-flowable
shell. In these embodiments the removal 205 can be effected by
pulling the pullable core out through an open end of the shell.
[0331] The method ends at 206.
[0332] FIGS. 12A and 12B are schematic illustrations of a tubular
structure 300 according to some embodiments of the present
invention. Tubular structure 300 is preferably fabricated by AM
(for example, by operating one of AM systems 10 and 110) from
building material formulations, for example, by executing selected
operations of method 200. In various exemplary embodiments of the
invention tubular structure 300 has a shape, and optionally and
preferably also mechanical properties, of a blood vessel. Tubular
structure 300 can comprise an elongated core 302 and a solid shell
308 encapsulating core 302.
[0333] In some embodiments, the smallest dimension of shell 308
(e.g., its outer diameter) is, from about 0.1 mm to about 5 cm, or
from about 1 mm to about 3 cm. In some embodiments, the wall
thickness of shell 308 is from about 0.1 mm to about 5 mm, or from
about 0.1 mm to about 3 mm. Other dimensions are also
contemplated.
[0334] Core 302 is optionally and preferably sacrificial. In some
optional and preferred embodiments, tubular structure 300 also
comprises an intermediate shell 304 between core 302 and shell 308.
In some optional and preferred embodiments, tubular structure 300
also comprises more than one intermediate shell between core 302
and shell 308. Embodiments in which tubular structure 300 comprises
a single intermediate shell are illustrated in FIG. 12A, and
embodiments in which tubular structure 300 comprises more than one
intermediate shells are illustrated in FIG. 12B (two such
intermediate shells 304 and 306 are shown in this exemplified
illustration, but any number of intermediate shells can be
included). The intermediate shell(s) are optionally and preferably
also sacrificial.
[0335] Each of core 302, shell 308 and the intermediate shells 304,
306 is optionally and preferably made of a different material or a
different combination of materials.
[0336] In some embodiments of the present invention shell 308
comprises hardened material M, as defined herein. Intermediate
shell 304 can comprise material FG. In some embodiments of the
present invention shell 304 comprises only material FG and is
devoid of other materials. Shell 306 can in some embodiments
comprises hardened material S.
[0337] Core 302 can be made in more than one way. In some
embodiments of the present invention core 302 is made of a digital
material that comprises material FG and material M, interlaced with
each other. These embodiments are particularly useful when it is
desired to fabricate tubular structures that have non uniform
diameter along their length. In some embodiments, core 302 is
formed of Material M, without interlacing it with an additional
material. In these embodiments core 302 is are pullable, and they
are particularly useful when it is desired to fabricate tubular
structures that have a generally uniform diameter (e.g., with
tolerance of less than 10%). The latter embodiments are also useful
when the shape of tubular structure 300 is intricate with
low-radius curves.
[0338] It is to be understood that other combinations of materials
can be used for structure 300. For example, in some embodiments of
the present invention, core 302 is made of hardened material FG,
and intermediate shell 304 can be made of hardened material S or a
digital material comprising hardened material S, as described
herein. The inventors found that such intermediate shell
significantly reduces the likelihood of inward collapse. Also
contemplated is a configuration in which core 302 is made of
hardened material FG, as defined herein, and intermediate shell 304
is made of a material L, as defined herein. The advantage of these
embodiments is that the non-solid intermediate shell 204 reduces
friction and therefor facilitates easy removal of core 302 from
tubular structure 300.
[0339] It was found by the Inventors that the quality of the
fabricated three-dimensional objects may be affected by the
orientation of parts of the object with respect to the direction of
the relative motion between the tray and the dispensing head. The
inventors have therefore devised a procedure in which the
orientation of the part of the object and the formulation or
combination of formulations that are used to fabricate this part
are selected based on each other. In particular, it was found that
a judicious selection of the formulation or formulations based on
the orientation of the part of the object can facilitate an easier
removal of the support material following the fabrication of the
object.
[0340] When the part of object is aligned generally along the
indexing direction (y or r) it is preferred to fabricate the core
using a digital material formulation which comprises an FG
formulation and a modeling material formulation M, where the M
formulation serves for reinforcing the FG formulation.
[0341] When the part of the object is aligned generally along the
scanning direction (x or q) it is preferred to fabricate the core
either using a FG formulation or using a digital material
formulation which comprises an FG formulation and a modeling
material formulation M, where the M formulation serves for
reinforcing the FG formulation.
[0342] Representative examples for the M formulations, include,
without limitation, any of the modeling materials marketed by
Stratasys, Israel, under the trade name Agilus.TM. family or
Vero.TM. family.
[0343] When the core is fabricated using a digital material
formulation which comprises an FG formulation and a modeling
material formulation M, the preferred voxel-level ratio between the
number of voxels p of formulation FG and the number of voxels q of
formulation M is from p:q of about 60:40 to p:q of about 80:20,
e.g., p:q of about 70:30.
[0344] The Inventor also discovered that when the part of the
object is fabricated using a digital material formulation, the
elementary units within the digital material formulation may affect
the mechanical properties of the fabricated part of the object. For
example, suppose that a digital material formulation includes a
first formulation (e.g., an M formulation) and a second formulation
(e.g., an FG formulation), where formulations are dispensed in a
manner that the first formulation forms a plurality of cubical
structures that are distributed within the second formulation, in a
manner that one or more, e.g., each, of the cubical structures of
the first formulation is surrounded by the second formulation. The
inventors found that the mechanical properties of the part can be
adjusted by a judicial selection of the orientation of the cubical
structures with respect to the scanning direction. In particular,
it was found that internal sacrificial parts are easier to be
removed when the cubical structures of the first formulation are at
an acute angle (for example, from about 20.degree. to about
70.degree., or from about 30.degree. to about 60.degree., e.g.,
about 45.degree.) relative to the scanning direction.
[0345] In a preferred embodiment, an object is formed to include a
core (e.g., core 302) a shell (e.g., shell 308) and one or more
intermediate shells (e.g., intermediate shells 304 and 396),
wherein the core of the object is fabricated using a digital
material formulation which comprises an FG formulation and a
modeling material formulation M, wherein the M formulation is
dispensed to form cubical structures that are oriented at an angle
of about 45.degree. with respect to the scanning direction (x or
.phi.), and wherein the intermediate shell is formed of a support
formulation S. This embodiment allows an easy removal of the core
and is particularly useful when the objects mimics a blood vessel.
Preferred sizes of the cubical structures is from about 0.5 to
about 1.5 mm along the main diagonal. Preferred thickness of the
intermediate shell is from about 0.01 mm to about 0.5 mm. The
preferred voxel-level ratio between the number of voxels p of
formulation FG in the core and the number of voxels q of
formulation M in the core is from p:q of about 60:40 to p:q of
about 80:20, e.g., p:q of about 70:30.
[0346] According to an aspect of some embodiments of the present
invention, there is provided a three-dimension model object
prepared by the method as described herein, in any of the
embodiments thereof and any combination thereof.
[0347] According to an aspect of some embodiments of the present
invention there is provided a 3D model object as described
herein.
[0348] While the above description of the system and method places
a particular emphasis on embodiments in which the layers are formed
by selective dispensing and curing of the building material
formulation (e.g., one or more modeling material formulations as
described herein and optionally a support material formulation), it
is to be understood that more detailed reference to such technique
is not to be interpreted as limiting the scope of the invention in
any way. For example, other practitioners in the field form the
layers by vat-based techniques, such as but not limited to,
stereolithography, and DLP (to this end see, e.g., in U.S. Pat.
Nos. 4,575,330 and 9,211,678 supra).
[0349] Thus, also contemplated are embodiments in which the system
comprises a vat-based system or apparatus, e.g., a
stereolithography or a DLP system or apparatus. As previously
indicated, a vat-based technique comprises a vat containing the
material which is exposed to a curing condition, typically is
irradiated by curing radiation, in a configured pattern
corresponding to the shape of a slice of the object, to form solid
objects by successively forming thin layers of a curable material
one on top of the other.
[0350] When the additive manufacturing utilizes stereolithography,
a programmed movable spot beam of curing radiation is directed on a
surface or layer of a curable fluid medium (one or more modeling
material formulations and optionally also a support material
formulation) to form a solid layer of the object at the surface.
Typically, the formulations are UV-curable formulations and the
curing radiation is UV radiation. Once a solid layer of the object
is formed, the layer is moved, in a programmed manner, away from
the fluid surface by the thickness of one layer and the next
cross-section is then formed and adhered to the immediately
preceding layer defining the object. This process is continued
until the entire object is formed.
[0351] When the additive manufacturing utilizes a DLP, a digital
light processor projects curing radiation which constitutes a
digital image of a slice of the object, preferably from below, to
form a solid layer of the object at the surface of the dispensed
layer of a curable formulation. Typically, the curable formulation
is a UV-curable formulation and the curing radiation is UV
radiation. Once a solid layer of the object is formed, the layer is
moved, in a programmed manner, away from the image plane of the
digital light processor by the thickness of one layer and the next
cross-section is then formed and adhered to the immediately
preceding layer defining the object. This process is continued
until the entire object is formed. It is expected that during the
life of a patent maturing from this application many relevant
curable and non-curable will be developed and the scope of the
materials described and claimed herein is intended to include all
such new technologies a priori.
[0352] As used herein the term "about" refers to .+-.10% or
.+-.5%.
[0353] The terms "comprises", "comprising", "includes",
"including", "having" and their conjugates mean "including but not
limited to".
[0354] The term "consisting of" means "including and limited
to".
[0355] The term "consisting essentially of" means that the
composition, method or structure may include additional
ingredients, steps and/or parts, but only if the additional
ingredients, steps and/or parts do not materially alter the basic
and novel characteristics of the claimed composition, method or
structure.
[0356] As used herein, the singular form "a", "an" and "the"
include plural references unless the context clearly dictates
otherwise. For example, the term "a compound" or "at least one
compound" may include a plurality of compounds, including mixtures
thereof.
[0357] Throughout this application, various embodiments of this
invention may be presented in a range format. It should be
understood that the description in range format is merely for
convenience and brevity and should not be construed as an
inflexible limitation on the scope of the invention. Accordingly,
the description of a range should be considered to have
specifically disclosed all the possible subranges as well as
individual numerical values within that range. For example,
description of a range such as from 1 to 6 should be considered to
have specifically disclosed subranges such as from 1 to 3, from 1
to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as
well as individual numbers within that range, for example, 1, 2, 3,
4, 5, and 6. This applies regardless of the breadth of the
range.
[0358] Whenever a numerical range is indicated herein, it is meant
to include any cited numeral (fractional or integral) within the
indicated range. The phrases "ranging/ranges between" a first
indicate number and a second indicate number and "ranging/ranges
from" a first indicate number "to" a second indicate number are
used herein interchangeably and are meant to include the first and
second indicated numbers and all the fractional and integral
numerals therebetween.
[0359] As used herein the term "method" refers to manners, means,
techniques and procedures for accomplishing a given task including,
but not limited to, those manners, means, techniques and procedures
either known to, or readily developed from known manners, means,
techniques and procedures by practitioners of the chemical,
pharmacological, biological, biochemical and medical arts.
[0360] Herein, the phrase "acrylic material" encompasses acrylate,
methacrylate, acrylamide and methacrylamide compounds.
[0361] Herein throughout, the term "(meth)acrylic" encompasses
acrylic and methacrylic compounds.
[0362] Herein, a liquid material L describes a liquid or
liquid-like material.
[0363] Herein throughout and in the art, the term "liquid"
describes a fluid that does not change its volume in response to
stress. Liquid materials are characterized by fluidity, that is,
the ability to flow as the molecules move by passing one by
another; a viscosity, that is, a resistance to shear stress; by
very low or zero shear modulus (G); and by a shear loss modulus to
shear storage modulus ratio (G''/G', or tan delta) higher than 1,
typically higher than 10.
[0364] Herein, a "liquid-like material" describes a material that
features properties similar to those of a liquid, by featuring, for
example, a low shear modulus, e.g., lower than 100 kPa or lower
than 50 kPa or lower than 10 kPa; and/or by a shear loss modulus to
shear storage modulus ratio (tan delta) higher than 1 as described
herein, optionally higher than 5 or higher than 10, and hence its
fluidity, viscosity and flowability resemble those of a liquid.
[0365] A liquid-like material can feature the above-mentioned
properties of a liquid upon application of shear forces. A
liquid-like material can be a shear-thinning material or a
thixotropic material, that is, a material that features a
shear-thinning behavior or thixotropy, respectively.
[0366] A liquid-like material can feature the above-mentioned
properties of a liquid upon application of heat energy. A
liquid-like material can be a thermal-thinning material, that is, a
material that features a thermal-thinning behavior.
[0367] A liquid-like material can have a consistency and/or
rheological properties of a gel or a paste.
[0368] Liquid and liquid-like materials can feature one or more of
the following characteristics: a viscosity of no more than 10000
centipoises; and/or Shear loss modulus to Shear storage modulus
ratio (tan delta) greater than 1; and/or Shear-thinning and/or
thixotropic behavior; and/or Thermal-thinning behavior; and/or a
Shear storage modulus lower than 20 kPa; and/or flowability when
subjected to a positive pressure lower than 1 bar or lower than 0.5
bar.
[0369] Shear storage modulus, G', is also referred to herein
interchangeably as "storage shear modulus", and reflects an elastic
behavior of a material. Liquid materials are typically non-elastic
and hence feature a low shear storage modulus.
[0370] Shear loss modulus, G'', is also referred to herein
interchangeably as "loss shear modulus", and reflects a viscous
behavior of a material.
[0371] Storage shear modulus and loss shear modulus may optionally
be determined using a shear rheometer, for example, a
strain-controlled rotational rheometer, at an indicated temperature
and frequency (e.g., using procedures well known in the art).
[0372] The Shear loss modulus to Shear storage modulus ratio,
G''/G', also known as "tan delta", reflects the viscoelastic
behavior of a material. Liquid materials are typically more viscous
and non-elastic and hence for liquids or liquid-like materials this
ratio is higher than 1. Gels are typically elastic and hence this
ratio for gel or gel-like materials is lower than 1.
[0373] Herein throughout, the term "shear-thinning" describes a
property of a fluidic compound or a material that is reflected by a
decrease in its viscosity (increase in its fluidity) upon
application of shear forces (under shear strain). In some of the
present embodiments, a shear-thinning material is such that
exhibits a significant, e.g., at least 100%, reduction in its Shear
modulus upon increasing the shear strain from about 1% to above
50%.
[0374] Herein throughout, the term "thixotropic" describes a
property of a fluidic compound or material that is reflected by a
time-dependent shear-thinning, that is its viscosity is decreased
in correlation with the time at which shear forces are applied, and
returns back to its original value when application of shear forces
is ceased. In some of the present embodiments, a thixotropic
material is such that exhibits a significant, e.g., at least 100%,
reduction in its Shear modulus under 50% strain.
[0375] Herein throughout, the term "thermal-thinning" describes a
property of a fluidic compound or a material that is reflected by a
decrease in its viscosity (increase in its fluidity) upon
application of heat energy (increase in temperature). In some of
the present embodiments, thermal-thinning materials feature a
decrease in viscosity or shear modulus by at least 20%, or at least
50%, or even 100%, upon being heated to a temperature of from 40 to
95.degree. C., including any intermediate value and subranges
therebetween.
[0376] Herein throughout, the phrase "linking moiety" or "linking
group" describes a group that connects two or more moieties or
groups in a compound. A linking moiety is typically derived from a
bi- or tri-functional compound, and can be regarded as a bi- or
tri-radical moiety, which is connected to two or three other
moieties, via two or three atoms thereof, respectively.
[0377] Exemplary linking moieties include a hydrocarbon moiety or
chain, optionally interrupted by one or more heteroatoms, as
defined herein, and/or any of the chemical groups listed below,
when defined as linking groups.
[0378] When a chemical group is referred to herein as "end group"
it is to be interpreted as a substituent, which is connected to
another group via one atom thereof.
[0379] Herein throughout, the term "hydrocarbon" collectively
describes a chemical group composed mainly of carbon and hydrogen
atoms. A hydrocarbon can be comprised of alkyl, alkene, alkyne,
aryl, and/or cycloalkyl, each can be substituted or unsubstituted,
and can be interrupted by one or more heteroatoms. The number of
carbon atoms can range from 2 to 20, and is preferably lower, e.g.,
from 1 to 10, or from 1 to 6, or from 1 to 4. A hydrocarbon can be
a linking group or an end group.
[0380] Bisphenol A is an example of a hydrocarbon comprised of 2
aryl groups and one alkyl group.
[0381] As used herein, the term "amine" describes both a --NR'R''
group and a --NR'-- group, wherein R' and R'' are each
independently hydrogen, alkyl, cycloalkyl, aryl, as these terms are
defined hereinbelow.
[0382] The amine group can therefore be a primary amine, where both
R' and R'' are hydrogen, a secondary amine, where R' is hydrogen
and R'' is alkyl, cycloalkyl or aryl, or a tertiary amine, where
each of R' and R'' is independently alkyl, cycloalkyl or aryl.
[0383] Alternatively, R' and R'' can each independently be
hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl,
heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,
phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,
thioaryloxy, cyano, nitro, azo, sulfonamide, carbonyl,
C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate,
urea, thiourea, N-carbamate, O-carbamate, C-amide, N-amide, guanyl,
guanidine and hydrazine.
[0384] The term "amine" is used herein to describe a --NR'R'' group
in cases where the amine is an end group, as defined hereinunder,
and is used herein to describe a --NW-- group in cases where the
amine is a linking group or is or part of a linking moiety.
[0385] The term "alkyl" describes a saturated aliphatic hydrocarbon
including straight chain and branched chain groups. Preferably, the
alkyl group has 1 to 30, or 1 to 20 carbon atoms. Whenever a
numerical range; e.g., "1-20", is stated herein, it implies that
the group, in this case the alkyl group, may contain 1 carbon atom,
2 carbon atoms, 3 carbon atoms, etc., up to and including 20 carbon
atoms. The alkyl group may be substituted or unsubstituted.
Substituted alkyl may have one or more substituents, whereby each
substituent group can independently be, for example, hydroxyalkyl,
trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl,
heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate,
hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy,
cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate,
N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate,
O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine.
[0386] The alkyl group can be an end group, as this phrase is
defined hereinabove, wherein it is attached to a single adjacent
atom, or a linking group, as this phrase is defined hereinabove,
which connects two or more moieties via at least two carbons in its
chain. When the alkyl is a linking group, it is also referred to
herein as "alkylene" or "alkylene chain".
[0387] Herein, a C(1-4) alkyl, substituted by a hydrophilic group,
as defined herein, is included under the phrase "hydrophilic group"
herein.
[0388] Alkene and Alkyne, as used herein, are an alkyl, as defined
herein, which contains one or more double bond or triple bond,
respectively.
[0389] The term "cycloalkyl" describes an all-carbon monocyclic
ring or fused rings (i.e., rings which share an adjacent pair of
carbon atoms) group where one or more of the rings does not have a
completely conjugated pi-electron system. Examples include, without
limitation, cyclohexane, adamantine, norbornyl, isobornyl, and the
like. The cycloalkyl group may be substituted or unsubstituted.
Substituted cycloalkyl may have one or more substituents, whereby
each substituent group can independently be, for example,
hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl,
heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,
phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,
thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,
O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,
N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine and
hydrazine. The cycloalkyl group can be an end group, as this phrase
is defined hereinabove, wherein it is attached to a single adjacent
atom, or a linking group, as this phrase is defined hereinabove,
connecting two or more moieties at two or more positions
thereof.
[0390] Cycloalkyls of 1-6 carbon atoms, substituted by two or more
hydrophilic groups, as defined herein, is included under the phrase
"hydrophilic group" herein.
[0391] The term "heteroalicyclic" describes a monocyclic or fused
ring group having in the ring(s) one or more atoms such as
nitrogen, oxygen and sulfur. The rings may also have one or more
double bonds. However, the rings do not have a completely
conjugated pi-electron system. Representative examples are
piperidine, piperazine, tetrahydrofurane, tetrahydropyrane,
morpholino, oxalidine, and the like.
[0392] The heteroalicyclic may be substituted or unsubstituted.
Substituted heteroalicyclic may have one or more substituents,
whereby each substituent group can independently be, for example,
hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl,
heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,
phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,
thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,
O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,
O-carbamate, N-carbamate, C-amide, N-amide, guanyl, guanidine and
hydrazine. The heteroalicyclic group can be an end group, as this
phrase is defined hereinabove, where it is attached to a single
adjacent atom, or a linking group, as this phrase is defined
hereinabove, connecting two or more moieties at two or more
positions thereof.
[0393] A heteroalicyclic group which includes one or more of
electron-donating atoms such as nitrogen and oxygen, and in which a
numeral ratio of carbon atoms to heteroatoms is 5:1 or lower, is
included under the phrase "hydrophilic group" herein.
[0394] The term "aryl" describes an all-carbon monocyclic or
fused-ring polycyclic (i.e., rings which share adjacent pairs of
carbon atoms) groups having a completely conjugated pi-electron
system. The aryl group may be substituted or unsubstituted.
Substituted aryl may have one or more substituents, whereby each
substituent group can independently be, for example, hydroxyalkyl,
trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl,
heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate,
hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy,
cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate,
N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate,
O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine. The
aryl group can be an end group, as this term is defined
hereinabove, wherein it is attached to a single adjacent atom, or a
linking group, as this term is defined hereinabove, connecting two
or more moieties at two or more positions thereof.
[0395] The term "heteroaryl" describes a monocyclic or fused ring
(i.e., rings which share an adjacent pair of atoms) group having in
the ring(s) one or more atoms, such as, for example, nitrogen,
oxygen and sulfur and, in addition, having a completely conjugated
pi-electron system. Examples, without limitation, of heteroaryl
groups include pyrrole, furan, thiophene, imidazole, oxazole,
thiazole, pyrazole, pyridine, pyrimidine, quinoline, isoquinoline
and purine. The heteroaryl group may be substituted or
unsubstituted. Substituted heteroaryl may have one or more
substituents, whereby each substituent group can independently be,
for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl,
alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide,
sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy,
thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo,
sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate,
O-thiocarbamate, urea, thiourea, O-carbamate, N-carbamate, C-amide,
N-amide, guanyl, guanidine and hydrazine. The heteroaryl group can
be an end group, as this phrase is defined hereinabove, where it is
attached to a single adjacent atom, or a linking group, as this
phrase is defined hereinabove, connecting two or more moieties at
two or more positions thereof. Representative examples are
pyridine, pyrrole, oxazole, indole, purine and the like.
[0396] The term "halide" and "halo" describes fluorine, chlorine,
bromine or iodine. The term "haloalkyl" describes an alkyl group as
defined above, further substituted by one or more halide.
[0397] The term "sulfate" describes a --O--S(.dbd.O).sub.2--OR' end
group, as this term is defined hereinabove, or an
--O--S(.dbd.O).sub.2--O-- linking group, as these phrases are
defined hereinabove, where R' is as defined hereinabove.
[0398] The term "thiosulfate" describes a
--O--S(.dbd.S)(.dbd.O)--OR' end group or a
--O--S(.dbd.S)(.dbd.O)--O-- linking group, as these phrases are
defined hereinabove, where R' is as defined hereinabove.
[0399] The term "sulfite" describes an --O--S(.dbd.O)--O--R' end
group or a --O--S(.dbd.O)--O-- group linking group, as these
phrases are defined hereinabove, where R' is as defined
hereinabove.
[0400] The term "thiosulfite" describes a --O--S(.dbd.S)--O--R' end
group or an --O--S(.dbd.S)--O-- group linking group, as these
phrases are defined hereinabove, where R' is as defined
hereinabove.
[0401] The term "sulfinate" describes a --S(.dbd.O)--OR' end group
or an --S(.dbd.O)--O-- group linking group, as these phrases are
defined hereinabove, where R' is as defined hereinabove.
[0402] The term "sulfoxide" or "sulfinyl" describes a --S(.dbd.O)R'
end group or an --S(.dbd.O)-- linking group, as these phrases are
defined hereinabove, where R' is as defined hereinabove.
[0403] The term "sulfonate" describes a --S(.dbd.O).sub.2--R' end
group or an --S(.dbd.O).sub.2-- linking group, as these phrases are
defined hereinabove, where R' is as defined herein.
[0404] The term "S-sulfonamide" describes a
--S(.dbd.O).sub.2--NR'R'' end group or a --S(.dbd.O).sub.2--NR'--
linking group, as these phrases are defined hereinabove, with R'
and R'' as defined herein.
[0405] The term "N-sulfonamide" describes an
R'S(.dbd.O).sub.2--NR''-- end group or a --S(.dbd.O).sub.2--NR'--
linking group, as these phrases are defined hereinabove, where R'
and R'' are as defined herein.
[0406] The term "disulfide" refers to a --S--SR' end group or a
--S--S-- linking group, as these phrases are defined hereinabove,
where R' is as defined herein.
[0407] The term "phosphonate" describes a --P(.dbd.O)(OR') (OR'')
end group or a --P(.dbd.O)(OR')(O)-- linking group, as these
phrases are defined hereinabove, with R' and R'' as defined
herein.
[0408] The term "thiophosphonate" describes a --P(.dbd.S)(OR')
(OR'') end group or a --P(.dbd.S)(OR')(O)-- linking group, as these
phrases are defined hereinabove, with R' and R'' as defined
herein.
[0409] The term "phosphinyl" describes a --PR'R'' end group or a
--PR'-- linking group, as these phrases are defined hereinabove,
with R' and R'' as defined hereinabove.
[0410] The term "phosphine oxide" describes a --P(.dbd.O)(R')(R'')
end group or a --P(.dbd.O)(R')-- linking group, as these phrases
are defined hereinabove, with R' and R'' as defined herein.
[0411] The term "phosphine sulfide" describes a
--P(.dbd.S)(R')(R'') end group or a --P(.dbd.S)(R')-- linking
group, as these phrases are defined hereinabove, with R' and R'' as
defined herein.
[0412] The term "phosphite" describes an --O--PR'(.dbd.O)(OR'') end
group or an --O--PH(.dbd.O)(O)-- linking group, as these phrases
are defined hereinabove, with R' and R'' as defined herein.
[0413] The term "carbonyl" or "carbonate" as used herein, describes
a --C(.dbd.O)--R' end group or a --C(.dbd.O)-- linking group, as
these phrases are defined hereinabove, with R' as defined
herein.
[0414] The term "thiocarbonyl" as used herein, describes a
--C(.dbd.S)--R' end group or a --C(.dbd.S)-- linking group, as
these phrases are defined hereinabove, with R' as defined
herein.
[0415] The term "oxo" as used herein, describes a (.dbd.O) group,
wherein an oxygen atom is linked by a double bond to the atom
(e.g., carbon atom) at the indicated position.
[0416] The term "thiooxo" as used herein, describes a (.dbd.S)
group, wherein a sulfur atom is linked by a double bond to the atom
(e.g., carbon atom) at the indicated position.
[0417] The term "oxime" describes a .dbd.N--OH end group or a
.dbd.N--O-- linking group, as these phrases are defined
hereinabove.
[0418] The term "hydroxyl" describes a --OH group.
[0419] The term "alkoxy" describes both an --O-alkyl and an
--O-cycloalkyl group, as defined herein.
[0420] The term "aryloxy" describes both an --O-aryl and an
--O-heteroaryl group, as defined herein.
[0421] The term "thiohydroxy" describes a --SH group.
[0422] The term "thioalkoxy" describes both a --S-alkyl group, and
a --S-cycloalkyl group, as defined herein.
[0423] The term "thioaryloxy" describes both a --S-aryl and a
--S-heteroaryl group, as defined herein.
[0424] The "hydroxyalkyl" is also referred to herein as "alcohol",
and describes an alkyl, as defined herein, substituted by a hydroxy
group.
[0425] The term "cyano" describes a --C.ident.N group.
[0426] The term "isocyanate" describes an --N.dbd.C.dbd.O
group.
[0427] The term "isothiocyanate" describes an --N.dbd.C.dbd.S
group.
[0428] The term "nitro" describes an --NO.sub.2 group.
[0429] The term "acyl halide" describes a --(C.dbd.O)R'''' group
wherein R'''' is halide, as defined hereinabove.
[0430] The term "azo" or "diazo" describes an --N.dbd.NR' end group
or an --N.dbd.N-- linking group, as these phrases are defined
hereinabove, with R' as defined hereinabove.
[0431] The term "peroxo" describes an --O--OR' end group or an
--O--O-- linking group, as these phrases are defined hereinabove,
with R' as defined hereinabove.
[0432] The term "carboxylate" as used herein encompasses
C-carboxylate and O-carboxylate.
[0433] The term "C-carboxylate" describes a --C(.dbd.O)--OR' end
group or a --C(.dbd.O)--O-- linking group, as these phrases are
defined hereinabove, where R' is as defined herein.
[0434] The term "O-carboxylate" describes a --OC(.dbd.O)R' end
group or a --OC(.dbd.O)-- linking group, as these phrases are
defined hereinabove, where R' is as defined herein.
[0435] A carboxylate can be linear or cyclic. When cyclic, R' and
the carbon atom are linked together to form a ring, in
C-carboxylate, and this group is also referred to as lactone.
Alternatively, R' and O are linked together to form a ring in
O-carboxylate. Cyclic carboxylates can function as a linking group,
for example, when an atom in the formed ring is linked to another
group.
[0436] The term "thiocarboxylate" as used herein encompasses
C-thiocarboxylate and O-thiocarboxylate.
[0437] The term "C-thiocarboxylate" describes a --C(.dbd.S)--OR'
end group or a --C(.dbd.S)--O-- linking group, as these phrases are
defined hereinabove, where R' is as defined herein.
[0438] The term "O-thiocarboxylate" describes a --OC(.dbd.S)R' end
group or a --OC(.dbd.S)-- linking group, as these phrases are
defined hereinabove, where R' is as defined herein.
[0439] A thiocarboxylate can be linear or cyclic. When cyclic, R'
and the carbon atom are linked together to form a ring, in
C-thiocarboxylate, and this group is also referred to as
thiolactone. Alternatively, R' and O are linked together to form a
ring in O-thiocarboxylate. Cyclic thiocarboxylates can function as
a linking group, for example, when an atom in the formed ring is
linked to another group.
[0440] The term "carbamate" as used herein encompasses N-carbamate
and O-carbamate.
[0441] The term "N-carbamate" describes an R''OC(.dbd.O)--NR'-- end
group or a --OC(.dbd.O)--NR'-- linking group, as these phrases are
defined hereinabove, with R' and R'' as defined herein. The term
"O-carbamate" describes an --OC(.dbd.O)--NR'R'' end group or an
--OC(.dbd.O)--NR'-- linking group, as these phrases are defined
hereinabove, with R' and R'' as defined herein.
[0442] A carbamate can be linear or cyclic. When cyclic, R' and the
carbon atom are linked together to form a ring, in O-carbamate.
Alternatively, R' and O are linked together to form a ring in
N-carbamate. Cyclic carbamates can function as a linking group, for
example, when an atom in the formed ring is linked to another
group.
[0443] The term "carbamate" as used herein encompasses N-carbamate
and O-carbamate.
[0444] The term "thiocarbamate" as used herein encompasses
N-thiocarbamate and O-thiocarbamate.
[0445] The term "O-thiocarbamate" describes a --OC(.dbd.S)--NR'R''
end group or a --OC(.dbd.S)--NR'-- linking group, as these phrases
are defined hereinabove, with R' and R'' as defined herein.
[0446] The term "N-thiocarbamate" describes an R''OC(.dbd.S)NR'--
end group or a --OC(.dbd.S)NR'-linking group, as these phrases are
defined hereinabove, with R' and R'' as defined herein.
[0447] Thiocarbamates can be linear or cyclic, as described herein
for carbamates.
[0448] The term "dithiocarbamate" as used herein encompasses
S-dithiocarbamate and N-dithiocarbamate.
[0449] The term "S-dithiocarbamate" describes a
--SC(.dbd.S)--NR'R'' end group or a --SC(.dbd.S)NR'-- linking
group, as these phrases are defined hereinabove, with R' and R'' as
defined herein.
[0450] The term "N-dithiocarbamate" describes an R''SC(.dbd.S)NR'--
end group or a --SC(.dbd.S)NR'-linking group, as these phrases are
defined hereinabove, with R' and R'' as defined herein.
[0451] The term "urea", which is also referred to herein as
"ureido", describes a --NR'C(.dbd.O)--NR''R''' end group or a
--NR'C(.dbd.O)--NR''-- linking group, as these phrases are defined
hereinabove, where R' and R'' are as defined herein and R''' is as
defined herein for R' and R''.
[0452] The term "thiourea", which is also referred to herein as
"thioureido", describes a --NR'--C(.dbd.S)--NR''R''' end group or a
--NR'--C(.dbd.S)--NR''-- linking group, with R', R'' and R''' as
defined herein.
[0453] The term "amide" as used herein encompasses C-amide and
N-amide.
[0454] The term "C-amide" describes a --C(.dbd.O)--NR'R'' end group
or a --C(.dbd.O)--NR'-- linking group, as these phrases are defined
hereinabove, where R' and R'' are as defined herein.
[0455] The term "N-amide" describes a R'C(.dbd.O)--NR''-- end group
or a R'C(.dbd.O)--N-- linking group, as these phrases are defined
hereinabove, where R' and R'' are as defined herein.
[0456] An amide can be linear or cyclic. When cyclic, R' and the
carbon atom are linked together to form a ring, in C-amide, and
this group is also referred to as lactam. Cyclic amides can
function as a linking group, for example, when an atom in the
formed ring is linked to another group.
[0457] The term "guanyl" describes a R'R''NC(.dbd.N)-- end group or
a --R'NC(.dbd.N)-- linking group, as these phrases are defined
hereinabove, where R' and R'' are as defined herein.
[0458] The term "guanidine" describes a --R'NC(.dbd.N)--NR''R'''
end group or a --R'NC(.dbd.N)-- NR''-- linking group, as these
phrases are defined hereinabove, where R', R'' and R''' are as
defined herein.
[0459] The term "hydrazine" describes a --NR'--NR''R''' end group
or a --NR'--NR''-- linking group, as these phrases are defined
hereinabove, with R', R'', and R''' as defined herein.
[0460] As used herein, the term "hydrazide" describes a
--C(.dbd.O)--NR'--NR''R''' end group or a --C(.dbd.O)--NR'--NR''--
linking group, as these phrases are defined hereinabove, where R',
R'' and R''' are as defined herein.
[0461] As used herein, the term "thiohydrazide" describes a
--C(.dbd.S)--NR'--NR''R''' end group or a --C(.dbd.S)--NR'--NR''--
linking group, as these phrases are defined hereinabove, where R',
R'' and R''' are as defined herein.
[0462] As used herein, the term "alkylene glycol" describes a
--O--[(CR'R'').sub.z--O].sub.yR''' end group or a
--O--[(CR'R'').sub.z--O].sub.y-- linking group, with R', R'' and
R''' being as defined herein, and with z being an integer of from 1
to 10, preferably, from 2 to 6, more preferably 2 or 3, and y being
an integer of 1 or more. Preferably R' and R'' are both hydrogen.
When z is 2 and y is 1, this group is ethylene glycol. When z is 3
and y is 1, this group is propylene glycol. When y is 2-4, the
alkylene glycol is referred to herein as oligo(alkylene
glycol).
[0463] When y is greater than 4, the alkylene glycol is referred to
herein as poly(alkylene glycol). In some embodiments of the present
invention, a poly(alkylene glycol) group or moiety can have from 10
to 200 repeating alkylene glycol units, such that z is 10 to 200,
preferably 10-100, more preferably 10-50.
[0464] The term "silanol" describes a --Si(OH)R'R'' group, or
--Si(OH).sub.2R' group or --Si(OH).sub.3 group, with R' and R'' as
described herein.
[0465] The term "silyl" describes a --SiR'R''R''' group, with R',
R'' and R''' as described herein.
[0466] As used herein, the term "urethane" or "urethane moiety" or
"urethane group" describes a Rx-O--C(.dbd.O)--NR'R'' end group or a
--Rx-O--C(.dbd.O)--NR'-- linking group, with R' and R'' being as
defined herein, and Rx being an alkyl, cycloalkyl, aryl, alkylene
glycol or any combination thereof. Preferably R' and R'' are both
hydrogen.
[0467] The term "polyurethane" or "oligourethane" describes a
moiety that comprises at least one urethane group as described
herein in the repeating backbone units thereof, or at least one
urethane bond, --O--C(.dbd.O)--NR'--, in the repeating backbone
units thereof.
[0468] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention, which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable subcombination
or as suitable in any other described embodiment of the invention.
Certain features described in the context of various embodiments
are not to be considered essential features of those embodiments,
unless the embodiment is inoperative without those elements.
[0469] Various embodiments and aspects of the present invention as
delineated hereinabove and as claimed in the claims section below
find experimental support in the following examples.
EXAMPLES
[0470] Reference is now made to the following examples, which
together with the above descriptions illustrate some embodiments of
the invention in a non limiting fashion.
Example 1
Flow Gel Formulations
[0471] Table 1 below presents the chemical compositions of
exemplary formulations that provide, when exposed to UV
irradiation, a flow gel formulation as defined herein.
TABLE-US-00001 TABLE 1 Percentage Component Exemplary Materials (%)
Monofunctional Poly(ethylene glycol) acrylate 3-10 curable material
Hydroxyalkyl acrylic material Multifunctional Multifunctional
Poly(alkylene 1-5 hydrophilic curable glycol)-containing acrylic
material material) Non-curable 1,2-Propanediol 80-90 material(s)
(Propylene glycol) 1,2,3-Propanetriol (Glycerol) Polypropylene
glycol (e.g., PPG600) Polyethylene glycol (e.g., PEG400) Propylene
carbonate Polyol 3165 Photoinitiator BAPO type (Bis Acyl 1-3
Phosphine Oxide) Alpha Hydroxy ketone MAPO (Monoacylphosphine
oxides) Surfactant/Dispersant BYK Type (PDMS 0-1 derivatives)
Inhibitor MEHQ 0.1-2 Genorad Type
[0472] All tested formulations feature viscosity at 75.degree. C.
of 10-30 (e.g., 10-15) centipoises, and surface tension at
25.degree. C. of 20-50 (e.g., 30-40) mN/m.sup.2. The formulations
were successfully used in 3D inkjet printing (are jettable), with
no curling of the printed object.
[0473] Shelf-life stability of the formulations was assessed by
measuring the viscosity and surface tension after storage at
65.degree. C. for 14 days. No change in viscosity and surface
tension was observed. The stability of the formulation as measured
in these tests, during 14 days, is indicative of a stability of the
formulation when stored at room temperature for 8 months.
[0474] Models printed using these formulations exhibited Young's
modulus values, as determined e.g. by ASTM E111, of less than 0.1
MPa, typically around 0.05 MPa.+-.20%.
[0475] It is to be noted that formulations comprising
monofunctional curable materials in an amount of 10-15% by weight,
but were lacking a multifunctional curable material provided
materials that did not meet jettability requirements of for some
inkjet AM systems, and produced hardened materials that were for
example, too sticky (data not shown).
[0476] A formulation as presented in Table 1 and described herein
is also referred to as FLG.
[0477] The solubility of the formulations was tested by immersing a
40.times.20.times.10 mm cube printed using the formulations, made
of a hardened in 2% NaOH aqueous solution.
[0478] Solubility was measured either for objects made of a single
formulation e (S), or of a mixture of two formulations, either two
support formulations or a support formulation and a model
formulation such as Agilus.TM. or Vero.TM. such that a core made of
the FG formulation was coated with 1 mm layer of the other
formulation (DM). Coated objects were tested upon cutting a
40.times.10 mm sidewall, for exposing the core (as shown, for
example, in FIG. 5).
[0479] The commercially available SUP706 formulation was used for
reference as a single support formulation (S).
[0480] Tables 2A and 2B below present the dissolution times
observed for each of the tested objects with (Table 2A) and without
(Table 2B) stirring.
TABLE-US-00002 TABLE 2A Time to complete dissolution Formulation
Type (minutes) FLG S 50 SUP706 S 230 FLG/SUP706 (1:1) DM 65
FLG/Agilus (1:1) DM 110 FLG/Vero (1:1) DM 95
TABLE-US-00003 TABLE 2B Time to complete dissolution Formulation
Type (hour) FLG S 1 SUP706 S 96 FLG/SUP706 DM 72 (75:25) FLG/SUP706
DM 72 (50:50) FLG/SUP706 DM 72 (25:75)
[0481] Additional objects, 40.times.20.times.10 mm cubes, were
printed in a DM mode in which a DM core was made of an FG
formulation having therein a grid made of a model formulation
(e.g., Agilus.TM.), and a coating of about 1 mm thickness was made
of the model formulation (Agilus.TM.)
[0482] FIG. 5 presents photographs showing such a printed object
(right photograph) and of the object during (middle photograph) and
after (left photograph) dissolution of the core in a 2% NaOH
solution. The sidewall of the object was cut before dissolution was
effected.
Example 2
3D Inkjet Printed Objects
[0483] When the object is aligned generally along the x direction
good results were achieved by printing a core made of an FG
formulation or a DM core made of an FG formulation reinforced with
a grid made of a modeling material formulation M as described
herein (e.g., Agilus, Vero). When the object is aligned generally
along the y direction good results were achieved by printing a DM
core made of an FG formulation reinforced with a grid made of a
modeling material formulation M as described herein. DM structure
was composed of about 30% grid of material M and about 70% of
material FG. One preferred DM structure (easy to clean) for
printing within the internal space of blood vessel mimics is made
of FG material with pre-set grid made of Agilus cubes, 0.5-1.5 mm
in diameter, oriented at an angle of about 45.degree. with respect
to the tray, and a thin (.ltoreq.0.5 mm) outline of SUP706. Optimal
jetting temperature of material FG is between 65-75.degree. C.
[0484] It was found by the Inventors that when a modeling material
formulation was embedded during the printing within an embedding
material, the mechanical properties of the modeling material
formulation were modified by the embedding material, even after the
embedding material is removed. To further investigate this
phenomenon, the ability of four types of embedding materials to
modify the mechanical properties of Agilus.TM. were tested. The
tested embedding materials were a first exemplary FG formulation
according to the present embodiments which comprises hydrophilic
curable materials that provide, when hardened per se water
insoluble material (referred to as FLG334A), a second exemplary FG
formulation according to the present embodiments which comprises
hydrophilic curable materials that provide, when hardened per se,
water soluble material (referred to as FLG-PA4), a support
formulation SUP706 or a Liquid formulation (which provides a liquid
or liquid-like material upon exposure to a curing condition.
[0485] To this end, "Dog bones" models made of Agilus.TM. as the
model material were printed on J750 (Stratasys Ltd., Israel) in
High Mix mode, such that the arms of the bone were supported by
support material SUP706, and the hinge of the bone was embedded
within the embedding material under investigation. This is
schematically illustrated in FIG. 7A. The Agilus.TM. model material
is shown at 710, the support material is shown at 712 and the
embedding material is shown at 714. FIG. 7B illustrates the
fabricated dog bone model following the removal of the support
material. The Agilus.TM. model material, once modified by the
embedding material 714, is shown at 716. FIG. 7C illustrates the
fabricated dog bone model following the removal of the embedding
material. The unmodified (710) and modified (716) Agilus.TM. model
materials are illustrated in FIGS. 7B and 7C using different line
patterns. The Stress-Strain curve of the modified Agilus was
measured, and the results, for the four tested types of embedding
material are shown in FIG. 8. As shown therein, FLG334A provides
the obtained model with better mechanical properties than the
reference formulation SUP706, the liquid, and the PA4
formulation.
[0486] FIGS. 6A and 6B present two DM printing modes utilizing a FG
support material formulation according to the present embodiments.
Both FIGS. 6A and 6B illustrate a structure 600 having a tubular
core 602 and one or more shells 604, 606, 608 surrounding core
602.
[0487] Preferably structure 600 comprises core 600 and shells 604
and 608. Optionally, structure 600 also comprises shell 606 between
shells 604 and 608. Shell 608 is the outermost shell and typically
comprises a material M such as Agilus.TM.. Shell 604 is adjacent to
core 602 and typically comprises only material FG. Optional shell
606 typically comprises a support material S such as SUP706. FIG.
6A illustrates an embodiment, referred to herein as Geometry 1, in
which core 602 is formed of material FG reinforced by material M
(e.g., Agilus.TM.). Material FG and Material M are typically
dispensed in an interlaced manner to form a digital material as
described herein. FIG. 6B illustrates an embodiment, referred to
herein as Geometry 2, in which core 602 is formed of Material M. In
this embodiment a pullable core 602 is formed, as demonstrated
below (see FIGS. 10 and 11).
[0488] Printing according to the embodiment illustrated in FIG. 6A
is particularly useful when it is desired to fabricate hollow
tubular structures that have non uniform diameter along their
length. Printing according to the embodiment illustrated in FIG. 6B
is particularly useful when it is desired to fabricate hollow
tubular structures that generally feature uniform diameter, and may
also be used for intricate tubular shapes having low-radius
curves.
[0489] FIG. 9 presents photographs demonstrating the support
material removal from an object made according to Geometry 1 mode
as shown in FIG. 6A using an FG formulation according to the
present embodiments. As shown therein, by application of small
pressure, the hardened support material is easily removed to
thereby reveal a hollow tubular structure.
[0490] Printing according to Geometry 2 as shown in FIG. 6B is
usable when printing models having hollow structures of intricate
geometries (e.g., twisted thin tunnels).
[0491] FIG. 10 presents photographs demonstrating the support
material removal from an object made according to Geometry 2 mode
using an FG formulation according to the present embodiments. As
shown therein, by application of small pressure, the hardened
support material is easily removed to thereby reveal a hollow
tubular structure.
[0492] FIG. 11 presents photographs demonstrating the support
material removal from an object made according to FIG. 6B according
to the present embodiments.
[0493] Although the invention has been described in conjunction
with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims.
[0494] All publications, patents and patent applications mentioned
in this specification are herein incorporated in their entirety by
reference into the specification, to the same extent as if each
individual publication, patent or patent application was
specifically and individually indicated to be incorporated herein
by reference. In addition, citation or identification of any
reference in this application shall not be construed as an
admission that such reference is available as prior art to the
present invention. To the extent that section headings are used,
they should not be construed as necessarily limiting.
[0495] In addition, any priority document(s) of this application
is/are hereby incorporated herein by reference in its/their
entirety.
* * * * *